On 21.02.24 17:02, Matthew Cassell wrote:
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 <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: 1141, comm: a.out, pages: 262145, not
enough memory for the allocation
Signed-off-by: Matthew Cassell <mcassell411@xxxxxxxxx>
---
mm/util.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/util.c b/mm/util.c
index 5a6a9802583b..c0afb56f16ea 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -976,8 +976,8 @@ 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);
+ pr_warn_ratelimited("%s: pid: %d, comm: %s, pages: %ld, not enough memory for the allocation\n",
+ __func__, current->pid, current->comm, pages);
vm_unacct_memory(pages);
return -ENOMEM;
I wonder if "bytes"/"kbytes" instead of pages would be more appropriate
here.
Often, this will fail due to mmap() [where we pass a size from user
space] and also "vm.overcommit_kbytes" is not in pages.
--
Cheers,
David / dhildenb
