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

["azurIt" <azurit@pobox.sk>]

>On Tue, Sep 10, 2013 at 09:32:53PM +0200, azurIt wrote:
>> >On Tue, Sep 10, 2013 at 08:13:59PM +0200, azurIt wrote:
>> >> >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@linux-foundation.org>, "Michal Hocko" <mhocko@suse.cz>, "David Rientjes" <rientjes@google.com>, "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>, "KOSAKI Motohiro" <kosaki.motohiro@jp.fujitsu.com>, linux-mm@kvack.org, cgroups@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
>> >> >> >> >> >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!
>> >> 
>> >> 
>> >> Johannes,
>> >> 
>> >> the server went down early in the morning, the symptoms were similar as before - huge I/O. Can't tell what exactly happened since I wasn't able to login even on the console. But I have some info:
>> >>  - applications were able to write to HDD so it wasn't deadlocked as before
>> >>  - here is how it looked on graphs: http://watchdog.sk/lkml/graphs.jpg
>> >>  - server wasn't responding from 6:36, it was down between 6:54 and 7:02 (i had to hard reboot it), I was awoken at 6:36 by really creepy sound from my phone ;)
>> >>  - my 'load check' script successfully killed apache at 6:41 but it didn't help as you can see
>> >>  - i have one screen with info from atop from time 6:44, looks like i/o was done by init (??!): http://watchdog.sk/lkml/atop.jpg (ignore swap warning, i have no swap)
>> >>  - also other type of logs are available
>> >>  - nothing like this happened before
>> >
>> >That IO from init looks really screwy, I have no idea what's going on
>> >on that machine, but it looks like there is more than just a memcg
>> >problem...  Any chance your thirdparty security patches are concealing
>> >kernel daemon activity behind the init process and the IO is actually
>> >coming from a kernel thread like the flushers or kswapd?
>> 
>> 
>> 
>> 
>> I really cannot tell but I never ever saw this before and i'm using all of my patches for several years. Here are all patches which i'm using right now (+ your patch):
>> http://watchdog.sk/lkml/patches3
>> 
>> 
>> 
>> 
>> >Are there OOM kill messages in the syslog?
>> 
>> 
>> 
>> Here is full kernel log between 6:00 and 7:59:
>> http://watchdog.sk/lkml/kern6.log
>
>Wow, your apaches are like the hydra.  Whenever one is OOM killed,
>more show up!



Yeah, it's supposed to do this ;)



>> >> What do you think? I'm now running kernel with your previous patch, not with the newest one.
>> >
>> >Which one exactly?  Can you attach the diff?
>> 
>> 
>> 
>> I meant, the problem above occured on kernel with your latest patch:
>> http://watchdog.sk/lkml/7-2-memcg-fix.patch
>
>The above log has the following callstack:
>
>Sep 10 07:59:43 server01 kernel: [ 3846.337628]  [<ffffffff810d19fe>] dump_header+0x7e/0x1e0
>Sep 10 07:59:43 server01 kernel: [ 3846.337707]  [<ffffffff810d18ff>] ? find_lock_task_mm+0x2f/0x70
>Sep 10 07:59:43 server01 kernel: [ 3846.337790]  [<ffffffff810d18ff>] ? find_lock_task_mm+0x2f/0x70
>Sep 10 07:59:43 server01 kernel: [ 3846.337874]  [<ffffffff81094bb0>] ? __css_put+0x50/0x90
>Sep 10 07:59:43 server01 kernel: [ 3846.337952]  [<ffffffff810d1ec5>] oom_kill_process+0x85/0x2a0
>Sep 10 07:59:43 server01 kernel: [ 3846.338037]  [<ffffffff810d2448>] mem_cgroup_out_of_memory+0xa8/0xf0
>Sep 10 07:59:43 server01 kernel: [ 3846.338120]  [<ffffffff81110858>] T.1154+0x8b8/0x8f0
>Sep 10 07:59:43 server01 kernel: [ 3846.338201]  [<ffffffff81110fa6>] mem_cgroup_charge_common+0x56/0xa0
>Sep 10 07:59:43 server01 kernel: [ 3846.338283]  [<ffffffff81111035>] mem_cgroup_newpage_charge+0x45/0x50
>Sep 10 07:59:43 server01 kernel: [ 3846.338364]  [<ffffffff810f3039>] handle_pte_fault+0x609/0x940
>Sep 10 07:59:43 server01 kernel: [ 3846.338451]  [<ffffffff8102ab1f>] ? pte_alloc_one+0x3f/0x50
>Sep 10 07:59:43 server01 kernel: [ 3846.338532]  [<ffffffff8107e455>] ? sched_clock_local+0x25/0x90
>Sep 10 07:59:43 server01 kernel: [ 3846.338617]  [<ffffffff810f34d7>] handle_mm_fault+0x167/0x340
>Sep 10 07:59:43 server01 kernel: [ 3846.338699]  [<ffffffff8102714b>] do_page_fault+0x13b/0x490
>Sep 10 07:59:43 server01 kernel: [ 3846.338781]  [<ffffffff810f8848>] ? do_brk+0x208/0x3a0
>Sep 10 07:59:43 server01 kernel: [ 3846.338865]  [<ffffffff812dba22>] ? gr_learn_resource+0x42/0x1e0
>Sep 10 07:59:43 server01 kernel: [ 3846.338951]  [<ffffffff815cb7bf>] page_fault+0x1f/0x30
>
>The charge code seems to be directly invoking the OOM killer, which is
>not possible with 7-2-memcg-fix.  Are you sure this is the right patch
>for this log?  This _looks_ more like what 7-1-memcg-fix was doing,
>with a direct kill in the charge context and a fixup later on.




I, luckyly, still have the kernel source from which that kernel was build. I tried to re-apply the 7-2-memcg-fix.patch:

# patch -p1 --dry-run < 7-2-memcg-fix.patch 
patching file arch/x86/mm/fault.c
Reversed (or previously applied) patch detected!  Assume -R? [n] 
Apply anyway? [n] 
Skipping patch.
4 out of 4 hunks ignored -- saving rejects to file arch/x86/mm/fault.c.rej
patching file include/linux/memcontrol.h
Hunk #1 succeeded at 141 with fuzz 2 (offset 21 lines).
Hunk #2 succeeded at 391 with fuzz 1 (offset 39 lines).
patching file include/linux/mm.h
Reversed (or previously applied) patch detected!  Assume -R? [n] 
Apply anyway? [n] 
Skipping patch.
1 out of 1 hunk ignored -- saving rejects to file include/linux/mm.h.rej
patching file include/linux/sched.h
Reversed (or previously applied) patch detected!  Assume -R? [n] 
Apply anyway? [n] 
Skipping patch.
1 out of 1 hunk ignored -- saving rejects to file include/linux/sched.h.rej
patching file mm/memcontrol.c
Reversed (or previously applied) patch detected!  Assume -R? [n] 
Apply anyway? [n] 
Skipping patch.
10 out of 10 hunks ignored -- saving rejects to file mm/memcontrol.c.rej
patching file mm/memory.c
Reversed (or previously applied) patch detected!  Assume -R? [n] 
Apply anyway? [n] 
Skipping patch.
2 out of 2 hunks ignored -- saving rejects to file mm/memory.c.rej
patching file mm/oom_kill.c
Reversed (or previously applied) patch detected!  Assume -R? [n] 
Apply anyway? [n] 
Skipping patch.
1 out of 1 hunk ignored -- saving rejects to file mm/oom_kill.c.rej


Can you tell from this if the source has the right patch?



>It's somewhat eerie that you have to manually apply these patches
>because of grsec because I have no idea of knowing what the end result
>is, especially since you had compile errors in this area before.  Is
>grsec making changes to memcg code or why are these patches not
>applying cleanly?




The problem was in mm/memory.c (first hunk) because grsec added this:

        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;

+#ifdef CONFIG_PAX_SEGMEXEC
+        struct vm_area_struct *vma_m;
+#endif  

        if (unlikely(is_vm_hugetlb_page(vma)))



I'm not using PAX anyway so it shouldn't be used. This was the only rejection but there were lots of fuzz too - I wasn't considering it as a problem, should I?




>> but after i had to reboot the server i booted the kernel with your previous patch:
>> http://watchdog.sk/lkml/7-1-memcg-fix.patch
>
>This one still has the known memcg leak.



I know but it's the best I have which don't take down the server (yet).


azur