Am 09.06.22 um 16:21 schrieb Michal Hocko:
On Thu 09-06-22 16:10:33, Christian König wrote:
Am 09.06.22 um 14:57 schrieb Michal Hocko:
On Thu 09-06-22 14:16:56, Christian König wrote:
Am 09.06.22 um 11:18 schrieb Michal Hocko:
On Tue 31-05-22 11:59:57, Christian König wrote:
This gives the OOM killer an additional hint which processes are
referencing shmem files with potentially no other accounting for them.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
mm/shmem.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/mm/shmem.c b/mm/shmem.c
index 4b2fea33158e..a4ad92a16968 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2179,6 +2179,11 @@ unsigned long shmem_get_unmapped_area(struct file *file,
return inflated_addr;
}
+static long shmem_oom_badness(struct file *file)
+{
+ return i_size_read(file_inode(file)) >> PAGE_SHIFT;
+}
This doesn't really represent the in memory size of the file, does it?
Well the file could be partially or fully swapped out as anonymous memory or
the address space only sparse populated, but even then just using the file
size as OOM badness sounded like the most straightforward approach to me.
It covers hole as well, right?
Yes, exactly.
So let's say I have a huge sparse shmem file. I will get killed because
the oom_badness of such a file would be large as well...
Yes, correct. But I of hand don't see how we could improve that accounting.
What could happen is that the file is also mmaped and we double account.
Also the memcg oom handling could be considerably skewed if the file was
shared between more memcgs.
Yes, and that's one of the reasons why I didn't touched the memcg by this
and only affected the classic OOM killer.
oom_badness is for all oom handlers, including memcg. Maybe I have
misread an earlier patch but I do not see anything specific to global
oom handling.
As far as I can see the oom_badness() function is only used in
oom_kill.c and in procfs to return the oom score. Did I missed
something?
oom_kill.c implements most of the oom killer functionality. Memcg oom
killing is a part of that. Have a look at select_bad_process.
Ah! So mem_cgroup_scan_tasks() calls oom_evaluate_task for each task in
the control group.
Thanks for pointing that out, that was absolutely not obvious to me.
Is that a show stopper? How should we address this?
Christian.
