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sched_ext: Use shorter slice while bypassing

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While bypassing, tasks are scheduled in FIFO order which favors tasks that
hog CPUs. This can slow down e.g. unloading of the BPF scheduler. While
bypassing, guaranteeing timely forward progress is the main goal. There's no
point in giving long slices. Shorten the time slice used while bypassing
from 20ms to 5ms.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David Vernet <void@manifault.com>
This commit is contained in:
Tejun Heo 2024-09-26 12:56:46 -10:00
parent b7b3b2dbae
commit 6f34d8d382
1 changed files with 4 additions and 2 deletions
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6
kernel/sched/ext.c
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@ -9,6 +9,7 @@
#define SCX_OP_IDX(op) (offsetof(struct sched_ext_ops, op) / sizeof(void (*)(void))) #define SCX_OP_IDX(op) (offsetof(struct sched_ext_ops, op) / sizeof(void (*)(void)))
enum scx_consts { enum scx_consts {
SCX_SLICE_BYPASS = SCX_SLICE_DFL / 4,
SCX_DSP_DFL_MAX_BATCH = 32, SCX_DSP_DFL_MAX_BATCH = 32,
SCX_DSP_MAX_LOOPS = 32, SCX_DSP_MAX_LOOPS = 32,
SCX_WATCHDOG_MAX_TIMEOUT = 30 * HZ, SCX_WATCHDOG_MAX_TIMEOUT = 30 * HZ,
@ -1944,6 +1945,7 @@ static bool scx_rq_online(struct rq *rq)
static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags, static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
int sticky_cpu) int sticky_cpu)
{ {
bool bypassing = scx_rq_bypassing(rq);
struct task_struct **ddsp_taskp; struct task_struct **ddsp_taskp;
unsigned long qseq; unsigned long qseq;
@ -1961,7 +1963,7 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
if (!scx_rq_online(rq)) if (!scx_rq_online(rq))
goto local; goto local;
if (scx_rq_bypassing(rq)) if (bypassing)
goto global; goto global;
if (p->scx.ddsp_dsq_id != SCX_DSQ_INVALID) if (p->scx.ddsp_dsq_id != SCX_DSQ_INVALID)
@ -2016,7 +2018,7 @@ local_norefill:
global: global:
touch_core_sched(rq, p); /* see the comment in local: */ touch_core_sched(rq, p); /* see the comment in local: */
p->scx.slice = SCX_SLICE_DFL; p->scx.slice = bypassing ? SCX_SLICE_BYPASS : SCX_SLICE_DFL;
dispatch_enqueue(find_global_dsq(p), p, enq_flags); dispatch_enqueue(find_global_dsq(p), p, enq_flags);
} }