From f5eec03611d9352c8b19134ecd4742a6ebc45282 Mon Sep 17 00:00:00 2001 From: Matthew Cassell Date: Thu, 22 Feb 2024 19:46:17 +0000 Subject: [PATCH] mm/util.c: add byte count to __vm_enough_memory failure warning Commit 44b414c8715c5dcf53288 ("mm/util.c: add warning if __vm_enough_memory fails") adds debug information which gives the process id and executable name should __vm_enough_memory() fail. Adding the number of pages to the failure message would benefit application developers and system administrators in debugging overambitious memory requests by providing a point of reference to the amount of memory causing __vm_enough_memory() to fail. 1. Set appropriate kernel tunable to reach code path for failure message: # echo 2 > /proc/sys/vm/overcommit_memory 2. Test program to generate failure - requests 1 gibibyte per iteration: #include #include int main(int argc, char **argv) { for(;;) { if(malloc(1<<30) == NULL) break; printf("allocated 1 GiB\n"); } return 0; } 3. Output: Before: __vm_enough_memory: pid: 1218, comm: a.out, not enough memory for the allocation After: __vm_enough_memory: pid: 1137, comm: a.out, bytes: 1073741824, not enough memory for the allocation Link: https://lkml.kernel.org/r/20240222194617.1255-1-mcassell411@gmail.com Signed-off-by: Matthew Cassell Cc: David Hildenbrand Signed-off-by: Andrew Morton --- mm/util.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/util.c b/mm/util.c index 5a6a9802583b..6710efaf1802 100644 --- a/mm/util.c +++ b/mm/util.c @@ -942,6 +942,7 @@ EXPORT_SYMBOL_GPL(vm_memory_committed); int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) { long allowed; + unsigned long bytes_failed; vm_acct_memory(pages); @@ -976,8 +977,9 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) if (percpu_counter_read_positive(&vm_committed_as) < allowed) return 0; error: - pr_warn_ratelimited("%s: pid: %d, comm: %s, not enough memory for the allocation\n", - __func__, current->pid, current->comm); + bytes_failed = pages << PAGE_SHIFT; + pr_warn_ratelimited("%s: pid: %d, comm: %s, bytes: %lu not enough memory for the allocation\n", + __func__, current->pid, current->comm, bytes_failed); vm_unacct_memory(pages); return -ENOMEM;