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... > > > 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. -- Michal Hocko SUSE Labs