From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751882Ab3IJVI7 (ORCPT ); Tue, 10 Sep 2013 17:08:59 -0400 Received: from gmmr8.centrum.cz ([46.255.227.254]:40960 "EHLO gmmr8.centrum.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751047Ab3IJVI4 (ORCPT ); Tue, 10 Sep 2013 17:08:56 -0400 To: =?utf-8?q?Johannes_Weiner?= Subject: =?utf-8?q?Re=3A_=5Bpatch_0=2F7=5D_improve_memcg_oom_killer_robustness_v2?= Date: Tue, 10 Sep 2013 23:08:53 +0200 From: "azurIt" Cc: =?utf-8?q?Andrew_Morton?= , =?utf-8?q?Michal_Hocko?= , =?utf-8?q?David_Rientjes?= , =?utf-8?q?KAMEZAWA_Hiroyuki?= , =?utf-8?q?KOSAKI_Motohiro?= , , , , , References: <20130903204850.GA1412@cmpxchg.org>, <20130904101852.58E70042@pobox.sk>, <20130905115430.GB856@cmpxchg.org>, <20130909151010.3A3CBC6A@pobox.sk>, <20130909172849.GG856@cmpxchg.org>, <20130909215917.96932098@pobox.sk>, <20130909201238.GH856@cmpxchg.org>, <20130910201359.D0984EFF@pobox.sk>, <20130910183740.GI856@cmpxchg.org>, <20130910213253.A1E666C5@pobox.sk> <20130910201222.GA25972@cmpxchg.org> In-Reply-To: <20130910201222.GA25972@cmpxchg.org> X-Mailer: Centrum Email 5.3 X-Priority: 3 X-Original-From: azurit@pobox.sk MIME-Version: 1.0 Message-Id: <20130910230853.FEEC19B5@pobox.sk> X-Maser: oho Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >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" , "Michal Hocko" , "David Rientjes" , "KAMEZAWA Hiroyuki" , "KOSAKI Motohiro" , 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] [] T.1154+0x622/0x8f0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715274] [] mem_cgroup_cache_charge+0xbe/0xe0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715357] [] add_to_page_cache_locked+0x4c/0x140 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715443] [] add_to_page_cache_lru+0x22/0x50 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715526] [] find_or_create_page+0x73/0xb0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715608] [] __getblk+0xea/0x2c0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715692] [] __bread+0x13/0xc0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715774] [] ext3_get_branch+0x98/0x140 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715859] [] ext3_get_blocks_handle+0xd7/0xdc0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715942] [] ext3_get_block+0xc4/0x120 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716023] [] do_mpage_readpage+0x38a/0x690 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716107] [] mpage_readpage+0x4f/0x70 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716188] [] ext3_readpage+0x28/0x60 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716268] [] filemap_fault+0x308/0x560 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716350] [] __do_fault+0x78/0x5a0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716433] [] 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] [] dump_header+0x7e/0x1e0 >Sep 10 07:59:43 server01 kernel: [ 3846.337707] [] ? find_lock_task_mm+0x2f/0x70 >Sep 10 07:59:43 server01 kernel: [ 3846.337790] [] ? find_lock_task_mm+0x2f/0x70 >Sep 10 07:59:43 server01 kernel: [ 3846.337874] [] ? __css_put+0x50/0x90 >Sep 10 07:59:43 server01 kernel: [ 3846.337952] [] oom_kill_process+0x85/0x2a0 >Sep 10 07:59:43 server01 kernel: [ 3846.338037] [] mem_cgroup_out_of_memory+0xa8/0xf0 >Sep 10 07:59:43 server01 kernel: [ 3846.338120] [] T.1154+0x8b8/0x8f0 >Sep 10 07:59:43 server01 kernel: [ 3846.338201] [] mem_cgroup_charge_common+0x56/0xa0 >Sep 10 07:59:43 server01 kernel: [ 3846.338283] [] mem_cgroup_newpage_charge+0x45/0x50 >Sep 10 07:59:43 server01 kernel: [ 3846.338364] [] handle_pte_fault+0x609/0x940 >Sep 10 07:59:43 server01 kernel: [ 3846.338451] [] ? pte_alloc_one+0x3f/0x50 >Sep 10 07:59:43 server01 kernel: [ 3846.338532] [] ? sched_clock_local+0x25/0x90 >Sep 10 07:59:43 server01 kernel: [ 3846.338617] [] handle_mm_fault+0x167/0x340 >Sep 10 07:59:43 server01 kernel: [ 3846.338699] [] do_page_fault+0x13b/0x490 >Sep 10 07:59:43 server01 kernel: [ 3846.338781] [] ? do_brk+0x208/0x3a0 >Sep 10 07:59:43 server01 kernel: [ 3846.338865] [] ? gr_learn_resource+0x42/0x1e0 >Sep 10 07:59:43 server01 kernel: [ 3846.338951] [] 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: "azurIt" Subject: =?utf-8?q?Re=3A_=5Bpatch_0=2F7=5D_improve_memcg_oom_killer_robustness_v2?= Date: Tue, 10 Sep 2013 23:08:53 +0200 Message-ID: <20130910230853.FEEC19B5@pobox.sk> References: <20130903204850.GA1412@cmpxchg.org>, <20130904101852.58E70042@pobox.sk>, <20130905115430.GB856@cmpxchg.org>, <20130909151010.3A3CBC6A@pobox.sk>, <20130909172849.GG856@cmpxchg.org>, <20130909215917.96932098@pobox.sk>, <20130909201238.GH856@cmpxchg.org>, <20130910201359.D0984EFF@pobox.sk>, <20130910183740.GI856@cmpxchg.org>, <20130910213253.A1E666C5@pobox.sk> <20130910201222.GA25972@cmpxchg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20130910201222.GA25972-druUgvl0LCNAfugRpC6u6w@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: =?utf-8?q?Johannes_Weiner?= Cc: =?utf-8?q?Andrew_Morton?= , =?utf-8?q?Michal_Hocko?= , =?utf-8?q?David_Rientjes?= , =?utf-8?q?KAMEZAWA_Hiroyuki?= , =?utf-8?q?KOSAKI_Motohiro?= , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-arch.vger.kernel.org >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" , "Michal Hocko" , "David Rientjes" , "KAMEZAWA Hiroyuki" , "KOSAKI Motohiro" , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.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] [] T.1154+0x622/0x8f0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715274] [] mem_cgroup_cache_charge+0xbe/0xe0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715357] [] add_to_page_cache_locked+0x4c/0x140 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715443] [] add_to_page_cache_lru+0x22/0x50 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715526] [] find_or_create_page+0x73/0xb0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715608] [] __getblk+0xea/0x2c0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715692] [] __bread+0x13/0xc0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715774] [] ext3_get_branch+0x98/0x140 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715859] [] ext3_get_blocks_handle+0xd7/0xdc0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715942] [] ext3_get_block+0xc4/0x120 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716023] [] do_mpage_readpage+0x38a/0x690 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716107] [] mpage_readpage+0x4f/0x70 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716188] [] ext3_readpage+0x28/0x60 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716268] [] filemap_fault+0x308/0x560 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716350] [] __do_fault+0x78/0x5a0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716433] [] 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] [] dump_header+0x7e/0x1e0 >Sep 10 07:59:43 server01 kernel: [ 3846.337707] [] ? find_lock_task_mm+0x2f/0x70 >Sep 10 07:59:43 server01 kernel: [ 3846.337790] [] ? find_lock_task_mm+0x2f/0x70 >Sep 10 07:59:43 server01 kernel: [ 3846.337874] [] ? __css_put+0x50/0x90 >Sep 10 07:59:43 server01 kernel: [ 3846.337952] [] oom_kill_process+0x85/0x2a0 >Sep 10 07:59:43 server01 kernel: [ 3846.338037] [] mem_cgroup_out_of_memory+0xa8/0xf0 >Sep 10 07:59:43 server01 kernel: [ 3846.338120] [] T.1154+0x8b8/0x8f0 >Sep 10 07:59:43 server01 kernel: [ 3846.338201] [] mem_cgroup_charge_common+0x56/0xa0 >Sep 10 07:59:43 server01 kernel: [ 3846.338283] [] mem_cgroup_newpage_charge+0x45/0x50 >Sep 10 07:59:43 server01 kernel: [ 3846.338364] [] handle_pte_fault+0x609/0x940 >Sep 10 07:59:43 server01 kernel: [ 3846.338451] [] ? pte_alloc_one+0x3f/0x50 >Sep 10 07:59:43 server01 kernel: [ 3846.338532] [] ? sched_clock_local+0x25/0x90 >Sep 10 07:59:43 server01 kernel: [ 3846.338617] [] handle_mm_fault+0x167/0x340 >Sep 10 07:59:43 server01 kernel: [ 3846.338699] [] do_page_fault+0x13b/0x490 >Sep 10 07:59:43 server01 kernel: [ 3846.338781] [] ? do_brk+0x208/0x3a0 >Sep 10 07:59:43 server01 kernel: [ 3846.338865] [] ? gr_learn_resource+0x42/0x1e0 >Sep 10 07:59:43 server01 kernel: [ 3846.338951] [] 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx106.postini.com [74.125.245.106]) by kanga.kvack.org (Postfix) with SMTP id 9466A6B0089 for ; Tue, 10 Sep 2013 17:08:55 -0400 (EDT) Subject: =?utf-8?q?Re=3A_=5Bpatch_0=2F7=5D_improve_memcg_oom_killer_robustness_v2?= Date: Tue, 10 Sep 2013 23:08:53 +0200 From: "azurIt" References: <20130903204850.GA1412@cmpxchg.org>, <20130904101852.58E70042@pobox.sk>, <20130905115430.GB856@cmpxchg.org>, <20130909151010.3A3CBC6A@pobox.sk>, <20130909172849.GG856@cmpxchg.org>, <20130909215917.96932098@pobox.sk>, <20130909201238.GH856@cmpxchg.org>, <20130910201359.D0984EFF@pobox.sk>, <20130910183740.GI856@cmpxchg.org>, <20130910213253.A1E666C5@pobox.sk> <20130910201222.GA25972@cmpxchg.org> In-Reply-To: <20130910201222.GA25972@cmpxchg.org> MIME-Version: 1.0 Message-Id: <20130910230853.FEEC19B5@pobox.sk> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: =?utf-8?q?Johannes_Weiner?= Cc: =?utf-8?q?Andrew_Morton?= , =?utf-8?q?Michal_Hocko?= , =?utf-8?q?David_Rientjes?= , =?utf-8?q?KAMEZAWA_Hiroyuki?= , =?utf-8?q?KOSAKI_Motohiro?= , linux-mm@kvack.org, cgroups@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org >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" , "Michal Hocko" , "David Rientjes" , "KAMEZAWA Hiroyuki" , "KOSAKI Motohiro" , 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] [] T.1154+0x622/0x8f0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715274] [] mem_cgroup_cache_charge+0xbe/0xe0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715357] [] add_to_page_cache_locked+0x4c/0x140 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715443] [] add_to_page_cache_lru+0x22/0x50 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715526] [] find_or_create_page+0x73/0xb0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715608] [] __getblk+0xea/0x2c0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715692] [] __bread+0x13/0xc0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715774] [] ext3_get_branch+0x98/0x140 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715859] [] ext3_get_blocks_handle+0xd7/0xdc0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.715942] [] ext3_get_block+0xc4/0x120 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716023] [] do_mpage_readpage+0x38a/0x690 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716107] [] mpage_readpage+0x4f/0x70 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716188] [] ext3_readpage+0x28/0x60 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716268] [] filemap_fault+0x308/0x560 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716350] [] __do_fault+0x78/0x5a0 >> >> >> >> > Aug 22 13:15:21 server01 kernel: [1251422.716433] [] 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] [] dump_header+0x7e/0x1e0 >Sep 10 07:59:43 server01 kernel: [ 3846.337707] [] ? find_lock_task_mm+0x2f/0x70 >Sep 10 07:59:43 server01 kernel: [ 3846.337790] [] ? find_lock_task_mm+0x2f/0x70 >Sep 10 07:59:43 server01 kernel: [ 3846.337874] [] ? __css_put+0x50/0x90 >Sep 10 07:59:43 server01 kernel: [ 3846.337952] [] oom_kill_process+0x85/0x2a0 >Sep 10 07:59:43 server01 kernel: [ 3846.338037] [] mem_cgroup_out_of_memory+0xa8/0xf0 >Sep 10 07:59:43 server01 kernel: [ 3846.338120] [] T.1154+0x8b8/0x8f0 >Sep 10 07:59:43 server01 kernel: [ 3846.338201] [] mem_cgroup_charge_common+0x56/0xa0 >Sep 10 07:59:43 server01 kernel: [ 3846.338283] [] mem_cgroup_newpage_charge+0x45/0x50 >Sep 10 07:59:43 server01 kernel: [ 3846.338364] [] handle_pte_fault+0x609/0x940 >Sep 10 07:59:43 server01 kernel: [ 3846.338451] [] ? pte_alloc_one+0x3f/0x50 >Sep 10 07:59:43 server01 kernel: [ 3846.338532] [] ? sched_clock_local+0x25/0x90 >Sep 10 07:59:43 server01 kernel: [ 3846.338617] [] handle_mm_fault+0x167/0x340 >Sep 10 07:59:43 server01 kernel: [ 3846.338699] [] do_page_fault+0x13b/0x490 >Sep 10 07:59:43 server01 kernel: [ 3846.338781] [] ? do_brk+0x208/0x3a0 >Sep 10 07:59:43 server01 kernel: [ 3846.338865] [] ? gr_learn_resource+0x42/0x1e0 >Sep 10 07:59:43 server01 kernel: [ 3846.338951] [] 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org