[LTP] [PATCH v1] swapon01.c: Apply a margin to avoid oom

[Wei Gao]

On Thu, Mar 14, 2024 at 02:40:40PM +0800, Li Wang wrote:
> Hi Wei,
> 
> On Thu, Mar 14, 2024 at 9:33 AM Wei Gao via ltp <ltp@lists.linux.it> wrote:
> 
> > During our test i find a oom error during test which triggered by
> > tst_pollute_memory.
> >
> > kernel:
> > oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),cpuset=/,mems_allowed=0-1,oom_memcg=/ltp/test-9552,task_memcg=/ltp/test-95520
> > kernel: Memory cgroup out of memory: Killed process 9575 (swapon01)
> > total-vm:1051484kB, anon-rss:1046572kB, file-rss:1280kB, shmem-rss:0k0
> >
> > Signed-off-by: Wei Gao <wegao@suse.com>
> > ---
> >  testcases/kernel/syscalls/swapon/swapon01.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/testcases/kernel/syscalls/swapon/swapon01.c
> > b/testcases/kernel/syscalls/swapon/swapon01.c
> > index d406e4bd9..357992525 100644
> > --- a/testcases/kernel/syscalls/swapon/swapon01.c
> > +++ b/testcases/kernel/syscalls/swapon/swapon01.c
> > @@ -41,7 +41,9 @@ static void setup(void)
> >         make_swapfile(SWAP_FILE, 10, 0);
> >
> >         SAFE_CG_PRINTF(tst_cg, "cgroup.procs", "%d", getpid());
> > -       SAFE_CG_PRINTF(tst_cg, "memory.max", "%lu", TESTMEM);
> > +
> > +       /* Apply a margin to avoid oom during tst_pollute_memory */
> > +       SAFE_CG_PRINTF(tst_cg, "memory.max", "%lu", TESTMEM + TESTMEM/100);
> >
> 
> Even with a bit of margin added there is still not guarantee to avoid OOM
> completely.
> 
> As the Cgroup V1 and V2 track memory and swap in two ways, if the margin is
> too large that might not make the swap happen which is not our expectation.
> 
> So other method I can think of is to disable the OOM in Cgoup,
>     echo 1 > memory.oom_control
This option not exist in cgroupv2, it seems no direct oom control for cgroupv2
> or, set `overcommit_memory` to 2 to prevent the OOM from occurring.
>     echo 2 > /proc/sys/vm/overcommit_memory
I have tried this option, oom still happen.
> 
> 
> 
> 
> >  }
> >
> >  static struct tst_test test = {
> > --
> > 2.35.3
> >
> >
> > --
> > Mailing list info: https://lists.linux.it/listinfo/ltp
> >
> >
> 
> -- 
> Regards,
> Li Wang