1
linux/tools/sched_ext/scx_simple.c

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sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
* Copyright (c) 2022 Tejun Heo <tj@kernel.org>
* Copyright (c) 2022 David Vernet <dvernet@meta.com>
*/
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <libgen.h>
#include <bpf/bpf.h>
#include <scx/common.h>
#include "scx_simple.bpf.skel.h"
const char help_fmt[] =
"A simple sched_ext scheduler.\n"
"\n"
"See the top-level comment in .bpf.c for more details.\n"
"\n"
sched_ext: Add vtime-ordered priority queue to dispatch_q's Currently, a dsq is always a FIFO. A task which is dispatched earlier gets consumed or executed earlier. While this is sufficient when dsq's are used for simple staging areas for tasks which are ready to execute, it'd make dsq's a lot more useful if they can implement custom ordering. This patch adds a vtime-ordered priority queue to dsq's. When the BPF scheduler dispatches a task with the new scx_bpf_dispatch_vtime() helper, it can specify the vtime tha the task should be inserted at and the task is inserted into the priority queue in the dsq which is ordered according to time_before64() comparison of the vtime values. A DSQ can either be a FIFO or priority queue and automatically switches between the two depending on whether scx_bpf_dispatch() or scx_bpf_dispatch_vtime() is used. Using the wrong variant while the DSQ already has the other type queued is not allowed and triggers an ops error. Built-in DSQs must always be FIFOs. This makes it very easy for the BPF schedulers to implement proper vtime based scheduling within each dsq very easy and efficient at a negligible cost in terms of code complexity and overhead. scx_simple and scx_example_flatcg are updated to default to weighted vtime scheduling (the latter within each cgroup). FIFO scheduling can be selected with -f option. v4: - As allowing mixing priority queue and FIFO on the same DSQ sometimes led to unexpected starvations, DSQs now error out if both modes are used at the same time and the built-in DSQs are no longer allowed to be priority queues. - Explicit type struct scx_dsq_node added to contain fields needed to be linked on DSQs. This will be used to implement stateful iterator. - Tasks are now always linked on dsq->list whether the DSQ is in FIFO or PRIQ mode. This confines PRIQ related complexities to the enqueue and dequeue paths. Other paths only need to look at dsq->list. This will also ease implementing BPF iterator. - Print p->scx.dsq_flags in debug dump. v3: - SCX_TASK_DSQ_ON_PRIQ flag is moved from p->scx.flags into its own p->scx.dsq_flags. The flag is protected with the dsq lock unlike other flags in p->scx.flags. This led to flag corruption in some cases. - Add comments explaining the interaction between using consumption of p->scx.slice to determine vtime progress and yielding. v2: - p->scx.dsq_vtime was not initialized on load or across cgroup migrations leading to some tasks being stalled for extended period of time depending on how saturated the machine is. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com>
2024-06-18 13:09:21 -07:00
"Usage: %s [-f] [-v]\n"
sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
"\n"
sched_ext: Add vtime-ordered priority queue to dispatch_q's Currently, a dsq is always a FIFO. A task which is dispatched earlier gets consumed or executed earlier. While this is sufficient when dsq's are used for simple staging areas for tasks which are ready to execute, it'd make dsq's a lot more useful if they can implement custom ordering. This patch adds a vtime-ordered priority queue to dsq's. When the BPF scheduler dispatches a task with the new scx_bpf_dispatch_vtime() helper, it can specify the vtime tha the task should be inserted at and the task is inserted into the priority queue in the dsq which is ordered according to time_before64() comparison of the vtime values. A DSQ can either be a FIFO or priority queue and automatically switches between the two depending on whether scx_bpf_dispatch() or scx_bpf_dispatch_vtime() is used. Using the wrong variant while the DSQ already has the other type queued is not allowed and triggers an ops error. Built-in DSQs must always be FIFOs. This makes it very easy for the BPF schedulers to implement proper vtime based scheduling within each dsq very easy and efficient at a negligible cost in terms of code complexity and overhead. scx_simple and scx_example_flatcg are updated to default to weighted vtime scheduling (the latter within each cgroup). FIFO scheduling can be selected with -f option. v4: - As allowing mixing priority queue and FIFO on the same DSQ sometimes led to unexpected starvations, DSQs now error out if both modes are used at the same time and the built-in DSQs are no longer allowed to be priority queues. - Explicit type struct scx_dsq_node added to contain fields needed to be linked on DSQs. This will be used to implement stateful iterator. - Tasks are now always linked on dsq->list whether the DSQ is in FIFO or PRIQ mode. This confines PRIQ related complexities to the enqueue and dequeue paths. Other paths only need to look at dsq->list. This will also ease implementing BPF iterator. - Print p->scx.dsq_flags in debug dump. v3: - SCX_TASK_DSQ_ON_PRIQ flag is moved from p->scx.flags into its own p->scx.dsq_flags. The flag is protected with the dsq lock unlike other flags in p->scx.flags. This led to flag corruption in some cases. - Add comments explaining the interaction between using consumption of p->scx.slice to determine vtime progress and yielding. v2: - p->scx.dsq_vtime was not initialized on load or across cgroup migrations leading to some tasks being stalled for extended period of time depending on how saturated the machine is. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com>
2024-06-18 13:09:21 -07:00
" -f Use FIFO scheduling instead of weighted vtime scheduling\n"
sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
" -v Print libbpf debug messages\n"
" -h Display this help and exit\n";
static bool verbose;
static volatile int exit_req;
static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
{
if (level == LIBBPF_DEBUG && !verbose)
return 0;
return vfprintf(stderr, format, args);
}
static void sigint_handler(int simple)
{
exit_req = 1;
}
static void read_stats(struct scx_simple *skel, __u64 *stats)
{
int nr_cpus = libbpf_num_possible_cpus();
__u64 cnts[2][nr_cpus];
__u32 idx;
memset(stats, 0, sizeof(stats[0]) * 2);
for (idx = 0; idx < 2; idx++) {
int ret, cpu;
ret = bpf_map_lookup_elem(bpf_map__fd(skel->maps.stats),
&idx, cnts[idx]);
if (ret < 0)
continue;
for (cpu = 0; cpu < nr_cpus; cpu++)
stats[idx] += cnts[idx][cpu];
}
}
int main(int argc, char **argv)
{
struct scx_simple *skel;
struct bpf_link *link;
__u32 opt;
sched_ext: Implement sched_ext_ops.cpu_online/offline() Add ops.cpu_online/offline() which are invoked when CPUs come online and offline respectively. As the enqueue path already automatically bypasses tasks to the local dsq on a deactivated CPU, BPF schedulers are guaranteed to see tasks only on CPUs which are between online() and offline(). If the BPF scheduler doesn't implement ops.cpu_online/offline(), the scheduler is automatically exited with SCX_ECODE_RESTART | SCX_ECODE_RSN_HOTPLUG. Userspace can implement CPU hotpplug support trivially by simply reinitializing and reloading the scheduler. scx_qmap is updated to print out online CPUs on hotplug events. Other schedulers are updated to restart based on ecode. v3: - The previous implementation added @reason to sched_class.rq_on/offline() to distinguish between CPU hotplug events and topology updates. This was buggy and fragile as the methods are skipped if the current state equals the target state. Instead, add scx_rq_[de]activate() which are directly called from sched_cpu_de/activate(). This also allows ops.cpu_on/offline() to sleep which can be useful. - ops.dispatch() could be called on a CPU that the BPF scheduler was told to be offline. The dispatch patch is updated to bypass in such cases. v2: - To accommodate lock ordering change between scx_cgroup_rwsem and cpus_read_lock(), CPU hotplug operations are put into its own SCX_OPI block and enabled eariler during scx_ope_enable() so that cpus_read_lock() can be dropped before acquiring scx_cgroup_rwsem. - Auto exit with ECODE added. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:20 -07:00
__u64 ecode;
sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
libbpf_set_print(libbpf_print_fn);
signal(SIGINT, sigint_handler);
signal(SIGTERM, sigint_handler);
sched_ext: Implement sched_ext_ops.cpu_online/offline() Add ops.cpu_online/offline() which are invoked when CPUs come online and offline respectively. As the enqueue path already automatically bypasses tasks to the local dsq on a deactivated CPU, BPF schedulers are guaranteed to see tasks only on CPUs which are between online() and offline(). If the BPF scheduler doesn't implement ops.cpu_online/offline(), the scheduler is automatically exited with SCX_ECODE_RESTART | SCX_ECODE_RSN_HOTPLUG. Userspace can implement CPU hotpplug support trivially by simply reinitializing and reloading the scheduler. scx_qmap is updated to print out online CPUs on hotplug events. Other schedulers are updated to restart based on ecode. v3: - The previous implementation added @reason to sched_class.rq_on/offline() to distinguish between CPU hotplug events and topology updates. This was buggy and fragile as the methods are skipped if the current state equals the target state. Instead, add scx_rq_[de]activate() which are directly called from sched_cpu_de/activate(). This also allows ops.cpu_on/offline() to sleep which can be useful. - ops.dispatch() could be called on a CPU that the BPF scheduler was told to be offline. The dispatch patch is updated to bypass in such cases. v2: - To accommodate lock ordering change between scx_cgroup_rwsem and cpus_read_lock(), CPU hotplug operations are put into its own SCX_OPI block and enabled eariler during scx_ope_enable() so that cpus_read_lock() can be dropped before acquiring scx_cgroup_rwsem. - Auto exit with ECODE added. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:20 -07:00
restart:
sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
skel = SCX_OPS_OPEN(simple_ops, scx_simple);
sched_ext: Add vtime-ordered priority queue to dispatch_q's Currently, a dsq is always a FIFO. A task which is dispatched earlier gets consumed or executed earlier. While this is sufficient when dsq's are used for simple staging areas for tasks which are ready to execute, it'd make dsq's a lot more useful if they can implement custom ordering. This patch adds a vtime-ordered priority queue to dsq's. When the BPF scheduler dispatches a task with the new scx_bpf_dispatch_vtime() helper, it can specify the vtime tha the task should be inserted at and the task is inserted into the priority queue in the dsq which is ordered according to time_before64() comparison of the vtime values. A DSQ can either be a FIFO or priority queue and automatically switches between the two depending on whether scx_bpf_dispatch() or scx_bpf_dispatch_vtime() is used. Using the wrong variant while the DSQ already has the other type queued is not allowed and triggers an ops error. Built-in DSQs must always be FIFOs. This makes it very easy for the BPF schedulers to implement proper vtime based scheduling within each dsq very easy and efficient at a negligible cost in terms of code complexity and overhead. scx_simple and scx_example_flatcg are updated to default to weighted vtime scheduling (the latter within each cgroup). FIFO scheduling can be selected with -f option. v4: - As allowing mixing priority queue and FIFO on the same DSQ sometimes led to unexpected starvations, DSQs now error out if both modes are used at the same time and the built-in DSQs are no longer allowed to be priority queues. - Explicit type struct scx_dsq_node added to contain fields needed to be linked on DSQs. This will be used to implement stateful iterator. - Tasks are now always linked on dsq->list whether the DSQ is in FIFO or PRIQ mode. This confines PRIQ related complexities to the enqueue and dequeue paths. Other paths only need to look at dsq->list. This will also ease implementing BPF iterator. - Print p->scx.dsq_flags in debug dump. v3: - SCX_TASK_DSQ_ON_PRIQ flag is moved from p->scx.flags into its own p->scx.dsq_flags. The flag is protected with the dsq lock unlike other flags in p->scx.flags. This led to flag corruption in some cases. - Add comments explaining the interaction between using consumption of p->scx.slice to determine vtime progress and yielding. v2: - p->scx.dsq_vtime was not initialized on load or across cgroup migrations leading to some tasks being stalled for extended period of time depending on how saturated the machine is. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com>
2024-06-18 13:09:21 -07:00
while ((opt = getopt(argc, argv, "fvh")) != -1) {
sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
switch (opt) {
sched_ext: Add vtime-ordered priority queue to dispatch_q's Currently, a dsq is always a FIFO. A task which is dispatched earlier gets consumed or executed earlier. While this is sufficient when dsq's are used for simple staging areas for tasks which are ready to execute, it'd make dsq's a lot more useful if they can implement custom ordering. This patch adds a vtime-ordered priority queue to dsq's. When the BPF scheduler dispatches a task with the new scx_bpf_dispatch_vtime() helper, it can specify the vtime tha the task should be inserted at and the task is inserted into the priority queue in the dsq which is ordered according to time_before64() comparison of the vtime values. A DSQ can either be a FIFO or priority queue and automatically switches between the two depending on whether scx_bpf_dispatch() or scx_bpf_dispatch_vtime() is used. Using the wrong variant while the DSQ already has the other type queued is not allowed and triggers an ops error. Built-in DSQs must always be FIFOs. This makes it very easy for the BPF schedulers to implement proper vtime based scheduling within each dsq very easy and efficient at a negligible cost in terms of code complexity and overhead. scx_simple and scx_example_flatcg are updated to default to weighted vtime scheduling (the latter within each cgroup). FIFO scheduling can be selected with -f option. v4: - As allowing mixing priority queue and FIFO on the same DSQ sometimes led to unexpected starvations, DSQs now error out if both modes are used at the same time and the built-in DSQs are no longer allowed to be priority queues. - Explicit type struct scx_dsq_node added to contain fields needed to be linked on DSQs. This will be used to implement stateful iterator. - Tasks are now always linked on dsq->list whether the DSQ is in FIFO or PRIQ mode. This confines PRIQ related complexities to the enqueue and dequeue paths. Other paths only need to look at dsq->list. This will also ease implementing BPF iterator. - Print p->scx.dsq_flags in debug dump. v3: - SCX_TASK_DSQ_ON_PRIQ flag is moved from p->scx.flags into its own p->scx.dsq_flags. The flag is protected with the dsq lock unlike other flags in p->scx.flags. This led to flag corruption in some cases. - Add comments explaining the interaction between using consumption of p->scx.slice to determine vtime progress and yielding. v2: - p->scx.dsq_vtime was not initialized on load or across cgroup migrations leading to some tasks being stalled for extended period of time depending on how saturated the machine is. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com>
2024-06-18 13:09:21 -07:00
case 'f':
skel->rodata->fifo_sched = true;
break;
sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
case 'v':
verbose = true;
break;
default:
fprintf(stderr, help_fmt, basename(argv[0]));
return opt != 'h';
}
}
sched_ext: Print debug dump after an error exit If a BPF scheduler triggers an error, the scheduler is aborted and the system is reverted to the built-in scheduler. In the process, a lot of information which may be useful for figuring out what happened can be lost. This patch adds debug dump which captures information which may be useful for debugging including runqueue and runnable thread states at the time of failure. The following shows a debug dump after triggering the watchdog: root@test ~# os/work/tools/sched_ext/build/bin/scx_qmap -t 100 stats : enq=1 dsp=0 delta=1 deq=0 stats : enq=90 dsp=90 delta=0 deq=0 stats : enq=156 dsp=156 delta=0 deq=0 stats : enq=218 dsp=218 delta=0 deq=0 stats : enq=255 dsp=255 delta=0 deq=0 stats : enq=271 dsp=271 delta=0 deq=0 stats : enq=284 dsp=284 delta=0 deq=0 stats : enq=293 dsp=293 delta=0 deq=0 DEBUG DUMP ================================================================================ kworker/u32:12[320] triggered exit kind 1026: runnable task stall (stress[1530] failed to run for 6.841s) Backtrace: scx_watchdog_workfn+0x136/0x1c0 process_scheduled_works+0x2b5/0x600 worker_thread+0x269/0x360 kthread+0xeb/0x110 ret_from_fork+0x36/0x40 ret_from_fork_asm+0x1a/0x30 QMAP FIFO[0]: QMAP FIFO[1]: QMAP FIFO[2]: 1436 QMAP FIFO[3]: QMAP FIFO[4]: CPU states ---------- CPU 0 : nr_run=1 ops_qseq=244 curr=swapper/0[0] class=idle_sched_class QMAP: dsp_idx=1 dsp_cnt=0 R stress[1530] -6841ms scx_state/flags=3/0x1 ops_state/qseq=2/20 sticky/holding_cpu=-1/-1 dsq_id=(n/a) cpus=ff QMAP: force_local=0 asm_sysvec_apic_timer_interrupt+0x16/0x20 CPU 2 : nr_run=2 ops_qseq=142 curr=swapper/2[0] class=idle_sched_class QMAP: dsp_idx=1 dsp_cnt=0 R sshd[1703] -5905ms scx_state/flags=3/0x9 ops_state/qseq=2/88 sticky/holding_cpu=-1/-1 dsq_id=(n/a) cpus=ff QMAP: force_local=1 __x64_sys_ppoll+0xf6/0x120 do_syscall_64+0x7b/0x150 entry_SYSCALL_64_after_hwframe+0x76/0x7e R fish[1539] -4141ms scx_state/flags=3/0x9 ops_state/qseq=2/124 sticky/holding_cpu=-1/-1 dsq_id=(n/a) cpus=ff QMAP: force_local=1 futex_wait+0x60/0xe0 do_futex+0x109/0x180 __x64_sys_futex+0x117/0x190 do_syscall_64+0x7b/0x150 entry_SYSCALL_64_after_hwframe+0x76/0x7e CPU 3 : nr_run=2 ops_qseq=162 curr=kworker/u32:12[320] class=ext_sched_class QMAP: dsp_idx=1 dsp_cnt=0 *R kworker/u32:12[320] +0ms scx_state/flags=3/0xd ops_state/qseq=0/0 sticky/holding_cpu=-1/-1 dsq_id=(n/a) cpus=ff QMAP: force_local=0 scx_dump_state+0x613/0x6f0 scx_ops_error_irq_workfn+0x1f/0x40 irq_work_run_list+0x82/0xd0 irq_work_run+0x14/0x30 __sysvec_irq_work+0x40/0x140 sysvec_irq_work+0x60/0x70 asm_sysvec_irq_work+0x16/0x20 scx_watchdog_workfn+0x15f/0x1c0 process_scheduled_works+0x2b5/0x600 worker_thread+0x269/0x360 kthread+0xeb/0x110 ret_from_fork+0x36/0x40 ret_from_fork_asm+0x1a/0x30 R kworker/3:2[1436] +0ms scx_state/flags=3/0x9 ops_state/qseq=2/160 sticky/holding_cpu=-1/-1 dsq_id=(n/a) cpus=08 QMAP: force_local=0 kthread+0xeb/0x110 ret_from_fork+0x36/0x40 ret_from_fork_asm+0x1a/0x30 CPU 7 : nr_run=0 ops_qseq=76 curr=swapper/7[0] class=idle_sched_class ================================================================================ EXIT: runnable task stall (stress[1530] failed to run for 6.841s) It shows that CPU 3 was running the watchdog when it triggered the error condition and the scx_qmap thread has been queued on CPU 0 for over 5 seconds but failed to run. It also prints out scx_qmap specific information - e.g. which tasks are queued on each FIFO and so on using the dump_*() ops. This dump has proved pretty useful for developing and debugging BPF schedulers. Debug dump is generated automatically when the BPF scheduler exits due to an error. The debug buffer used in such cases is determined by sched_ext_ops.exit_dump_len and defaults to 32k. If the debug dump overruns the available buffer, the output is truncated and marked accordingly. Debug dump output can also be read through the sched_ext_dump tracepoint. When read through the tracepoint, there is no length limit. SysRq-D can be used to trigger debug dump at any time while a BPF scheduler is loaded. This is non-destructive - the scheduler keeps running afterwards. The output can be read through the sched_ext_dump tracepoint. v2: - The size of exit debug dump buffer can now be customized using sched_ext_ops.exit_dump_len. - sched_ext_ops.dump*() added to enable dumping of BPF scheduler specific information. - Tracpoint output and SysRq-D triggering added. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com>
2024-06-18 13:09:18 -07:00
SCX_OPS_LOAD(skel, simple_ops, scx_simple, uei);
sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
link = SCX_OPS_ATTACH(skel, simple_ops, scx_simple);
while (!exit_req && !UEI_EXITED(skel, uei)) {
__u64 stats[2];
read_stats(skel, stats);
printf("local=%llu global=%llu\n", stats[0], stats[1]);
fflush(stdout);
sleep(1);
}
bpf_link__destroy(link);
sched_ext: Implement sched_ext_ops.cpu_online/offline() Add ops.cpu_online/offline() which are invoked when CPUs come online and offline respectively. As the enqueue path already automatically bypasses tasks to the local dsq on a deactivated CPU, BPF schedulers are guaranteed to see tasks only on CPUs which are between online() and offline(). If the BPF scheduler doesn't implement ops.cpu_online/offline(), the scheduler is automatically exited with SCX_ECODE_RESTART | SCX_ECODE_RSN_HOTPLUG. Userspace can implement CPU hotpplug support trivially by simply reinitializing and reloading the scheduler. scx_qmap is updated to print out online CPUs on hotplug events. Other schedulers are updated to restart based on ecode. v3: - The previous implementation added @reason to sched_class.rq_on/offline() to distinguish between CPU hotplug events and topology updates. This was buggy and fragile as the methods are skipped if the current state equals the target state. Instead, add scx_rq_[de]activate() which are directly called from sched_cpu_de/activate(). This also allows ops.cpu_on/offline() to sleep which can be useful. - ops.dispatch() could be called on a CPU that the BPF scheduler was told to be offline. The dispatch patch is updated to bypass in such cases. v2: - To accommodate lock ordering change between scx_cgroup_rwsem and cpus_read_lock(), CPU hotplug operations are put into its own SCX_OPI block and enabled eariler during scx_ope_enable() so that cpus_read_lock() can be dropped before acquiring scx_cgroup_rwsem. - Auto exit with ECODE added. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:20 -07:00
ecode = UEI_REPORT(skel, uei);
sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
scx_simple__destroy(skel);
sched_ext: Implement sched_ext_ops.cpu_online/offline() Add ops.cpu_online/offline() which are invoked when CPUs come online and offline respectively. As the enqueue path already automatically bypasses tasks to the local dsq on a deactivated CPU, BPF schedulers are guaranteed to see tasks only on CPUs which are between online() and offline(). If the BPF scheduler doesn't implement ops.cpu_online/offline(), the scheduler is automatically exited with SCX_ECODE_RESTART | SCX_ECODE_RSN_HOTPLUG. Userspace can implement CPU hotpplug support trivially by simply reinitializing and reloading the scheduler. scx_qmap is updated to print out online CPUs on hotplug events. Other schedulers are updated to restart based on ecode. v3: - The previous implementation added @reason to sched_class.rq_on/offline() to distinguish between CPU hotplug events and topology updates. This was buggy and fragile as the methods are skipped if the current state equals the target state. Instead, add scx_rq_[de]activate() which are directly called from sched_cpu_de/activate(). This also allows ops.cpu_on/offline() to sleep which can be useful. - ops.dispatch() could be called on a CPU that the BPF scheduler was told to be offline. The dispatch patch is updated to bypass in such cases. v2: - To accommodate lock ordering change between scx_cgroup_rwsem and cpus_read_lock(), CPU hotplug operations are put into its own SCX_OPI block and enabled eariler during scx_ope_enable() so that cpus_read_lock() can be dropped before acquiring scx_cgroup_rwsem. - Auto exit with ECODE added. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:20 -07:00
if (UEI_ECODE_RESTART(ecode))
goto restart;
sched_ext: Add scx_simple and scx_example_qmap example schedulers Add two simple example BPF schedulers - simple and qmap. * simple: In terms of scheduling, it behaves identical to not having any operation implemented at all. The two operations it implements are only to improve visibility and exit handling. On certain homogeneous configurations, this actually can perform pretty well. * qmap: A fixed five level priority scheduler to demonstrate queueing PIDs on BPF maps for scheduling. While not very practical, this is useful as a simple example and will be used to demonstrate different features. v7: - Compat helpers stripped out in prepartion of upstreaming as the upstreamed patchset will be the baselinfe. Utility macros that can be used to implement compat features are kept. - Explicitly disable map autoattach on struct_ops to avoid trying to attach twice while maintaining compatbility with older libbpf. v6: - Common header files reorganized and cleaned up. Compat helpers are added to demonstrate how schedulers can maintain backward compatibility with older kernels while making use of newly added features. - simple_select_cpu() added to keep track of the number of local dispatches. This is needed because the default ops.select_cpu() implementation is updated to dispatch directly and won't call ops.enqueue(). - Updated to reflect the sched_ext API changes. Switching all tasks is the default behavior now and scx_qmap supports partial switching when `-p` is specified. - tools/sched_ext/Kconfig dropped. This will be included in the doc instead. v5: - Improve Makefile. Build artifects are now collected into a separate dir which change be changed. Install and help targets are added and clean actually cleans everything. - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR() and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss. - Add scx_common.h which provides common utilities to user code such as SCX_BUG[_ON]() and RESIZE_ARRAY(). - Use SCX_BUG[_ON]() to simplify error handling. v4: - Dropped _example prefix from scheduler names. v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit to ease later additions. Comment updates. - Added declarations for BPF inline iterators. In the future, hopefully, these will be consolidated into a generic BPF header so that they don't need to be replicated here. v2: - Updated with the generic BPF cpumask helpers. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com>
2024-06-18 13:09:17 -07:00
return 0;
}