Commit f5eec036 authored by Matthew Cassell's avatar Matthew Cassell Committed by Andrew Morton
Browse files

mm/util.c: add byte count to __vm_enough_memory failure warning 

Commit 44b414c8 ("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 <stdlib.h>
	#include <stdio.h>

	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: default avatarMatthew Cassell <mcassell411@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 3fb43636

mm/util.c

+4 −2
Original line number Diff line number Diff line
@@ -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;