Re: [patch 0/7] improve memcg oom killer robustness v2

[Johannes Weiner]

On Mon, Sep 09, 2013 at 09:59:17PM +0200, azurIt wrote:
> >On Mon, Sep 09, 2013 at 03:10:10PM +0200, azurIt wrote:
> >> >Hi azur,
> >> >
> >> >On Wed, Sep 04, 2013 at 10:18:52AM +0200, azurIt wrote:
> >> >> > CC: "Andrew Morton" <akpm@xxxxxxxxxxxxxxxxxxxx>, "Michal Hocko" <mhocko@xxxxxxx>, "David Rientjes" <rientjes@xxxxxxxxxx>, "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@xxxxxxxxxxxxxx>, "KOSAKI Motohiro" <kosaki.motohiro@xxxxxxxxxxxxxx>, linux-mm@xxxxxxxxx, cgroups@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
> >> >> >Hello azur,
> >> >> >
> >> >> >On Mon, Sep 02, 2013 at 12:38:02PM +0200, azurIt wrote:
> >> >> >> >>Hi azur,
> >> >> >> >>
> >> >> >> >>here is the x86-only rollup of the series for 3.2.
> >> >> >> >>
> >> >> >> >>Thanks!
> >> >> >> >>Johannes
> >> >> >> >>---
> >> >> >> >
> >> >> >> >
> >> >> >> >Johannes,
> >> >> >> >
> >> >> >> >unfortunately, one problem arises: I have (again) cgroup which cannot be deleted :( it's a user who had very high memory usage and was reaching his limit very often. Do you need any info which i can gather now?
> >> >> >
> >> >> >Did the OOM killer go off in this group?
> >> >> >
> >> >> >Was there a warning in the syslog ("Fixing unhandled memcg OOM
> >> >> >context")?
> >> >> 
> >> >> 
> >> >> 
> >> >> Ok, i see this message several times in my syslog logs, one of them is also for this unremovable cgroup (but maybe all of them cannot be removed, should i try?). Example of the log is here (don't know where exactly it starts and ends so here is the full kernel log):
> >> >> http://watchdog.sk/lkml/oom_syslog.gz
> >> >There is an unfinished OOM invocation here:
> >> >
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715112] Fixing unhandled memcg OOM context set up from:
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715191]  [<ffffffff811105c2>] T.1154+0x622/0x8f0
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715274]  [<ffffffff8111153e>] mem_cgroup_cache_charge+0xbe/0xe0
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715357]  [<ffffffff810cf31c>] add_to_page_cache_locked+0x4c/0x140
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715443]  [<ffffffff810cf432>] add_to_page_cache_lru+0x22/0x50
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715526]  [<ffffffff810cfdd3>] find_or_create_page+0x73/0xb0
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715608]  [<ffffffff811493ba>] __getblk+0xea/0x2c0
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715692]  [<ffffffff8114ca73>] __bread+0x13/0xc0
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715774]  [<ffffffff81196968>] ext3_get_branch+0x98/0x140
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715859]  [<ffffffff81197557>] ext3_get_blocks_handle+0xd7/0xdc0
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.715942]  [<ffffffff81198304>] ext3_get_block+0xc4/0x120
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.716023]  [<ffffffff81155c3a>] do_mpage_readpage+0x38a/0x690
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.716107]  [<ffffffff81155f8f>] mpage_readpage+0x4f/0x70
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.716188]  [<ffffffff811973a8>] ext3_readpage+0x28/0x60
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.716268]  [<ffffffff810cfa48>] filemap_fault+0x308/0x560
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.716350]  [<ffffffff810ef898>] __do_fault+0x78/0x5a0
> >> >  Aug 22 13:15:21 server01 kernel: [1251422.716433]  [<ffffffff810f2ab4>] handle_pte_fault+0x84/0x940
> >> >
> >> >__getblk() has this weird loop where it tries to instantiate the page,
> >> >frees memory on failure, then retries.  If the memcg goes OOM, the OOM
> >> >path might be entered multiple times and each time leak the memcg
> >> >reference of the respective previous OOM invocation.
> >> >
> >> >There are a few more find_or_create() sites that do not propagate an
> >> >error and it's incredibly hard to find out whether they are even taken
> >> >during a page fault.  It's not practical to annotate them all with
> >> >memcg OOM toggles, so let's just catch all OOM contexts at the end of
> >> >handle_mm_fault() and clear them if !VM_FAULT_OOM instead of treating
> >> >this like an error.
> >> >
> >> >azur, here is a patch on top of your modified 3.2.  Note that Michal
> >> >might be onto something and we are looking at multiple issues here,
> >> >but the log excert above suggests this fix is required either way.
> >> 
> >> 
> >> 
> >> 
> >> Johannes, is this still up to date? Thank you.
> >
> >No, please use the following on top of 3.2 (i.e. full replacement, not
> >incremental to what you have):
> 
> 
> 
> Unfortunately it didn't compile:
> 
> 
> 
> 
>   LD      vmlinux.o
>   MODPOST vmlinux.o
> WARNING: modpost: Found 4924 section mismatch(es).
> To see full details build your kernel with:
> 'make CONFIG_DEBUG_SECTION_MISMATCH=y'
>   GEN     .version
>   CHK     include/generated/compile.h
>   UPD     include/generated/compile.h
>   CC      init/version.o
>   LD      init/built-in.o
>   LD      .tmp_vmlinux1
> arch/x86/built-in.o: In function `do_page_fault':
> (.text+0x26a77): undefined reference to `handle_mm_fault'
> mm/built-in.o: In function `fixup_user_fault':
> (.text+0x224d3): undefined reference to `handle_mm_fault'
> mm/built-in.o: In function `__get_user_pages':
> (.text+0x24a0f): undefined reference to `handle_mm_fault'
> make: *** [.tmp_vmlinux1] Error 1

Oops, sorry about that.  Must be configuration dependent because it
works for me (and handle_mm_fault is obviously defined).

Do you have warnings earlier in the compilation?  You can use make -s
to filter out everything but warnings.

Or send me your configuration so I can try to reproduce it here.

Thanks!

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