Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753693Ab3IRUw0 (ORCPT ); Wed, 18 Sep 2013 16:52:26 -0400 Received: from gmmr3.centrum.cz ([46.255.225.251]:37504 "EHLO gmmr3.centrum.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751873Ab3IRUwX (ORCPT ); Wed, 18 Sep 2013 16:52:23 -0400 To: =?utf-8?q?Johannes_Weiner?= Subject: =?utf-8?q?Re=3A_=5Bpatch_0=2F7=5D_improve_memcg_oom_killer_robustness_v2?= Date: Wed, 18 Sep 2013 22:52:19 +0200 From: "azurIt" Cc: =?utf-8?q?Michal_Hocko?= , =?utf-8?q?Andrew_Morton?= , =?utf-8?q?David_Rientjes?= , =?utf-8?q?KAMEZAWA_Hiroyuki?= , =?utf-8?q?KOSAKI_Motohiro?= , , , , , References: <20130916145744.GE3674@dhcp22.suse.cz>, <20130916170543.77F1ECB4@pobox.sk>, <20130916152548.GF3674@dhcp22.suse.cz>, <20130916225246.A633145B@pobox.sk>, <20130917000244.GD3278@cmpxchg.org>, <20130917131535.94E0A843@pobox.sk>, <20130917141013.GA30838@dhcp22.suse.cz>, <20130918160304.6EDF2729@pobox.sk>, <20130918180455.GD856@cmpxchg.org>, <20130918181946.GE856@cmpxchg.org> <20130918195504.GF856@cmpxchg.org> In-Reply-To: <20130918195504.GF856@cmpxchg.org> X-Mailer: Centrum Email 5.3 X-Priority: 3 X-Original-From: azurit@pobox.sk MIME-Version: 1.0 Message-Id: <20130918225219.670AD8C2@pobox.sk> X-Maser: Georgo 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 Content-Length: 6700 Lines: 122 > CC: "Michal Hocko" , "Andrew Morton" , "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 >On Wed, Sep 18, 2013 at 02:19:46PM -0400, Johannes Weiner wrote: >> On Wed, Sep 18, 2013 at 02:04:55PM -0400, Johannes Weiner wrote: >> > On Wed, Sep 18, 2013 at 04:03:04PM +0200, azurIt wrote: >> > > > CC: "Johannes Weiner" , "Andrew Morton" , "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 >> > > >On Tue 17-09-13 13:15:35, azurIt wrote: >> > > >[...] >> > > >> Is something unusual on this stack? >> > > >> >> > > >> >> > > >> [] dump_header+0x7e/0x1e0 >> > > >> [] ? find_lock_task_mm+0x2f/0x70 >> > > >> [] oom_kill_process+0x85/0x2a0 >> > > >> [] mem_cgroup_out_of_memory+0xa8/0xf0 >> > > >> [] mem_cgroup_oom_synchronize+0x2e6/0x310 >> > > >> [] ? mem_cgroup_uncharge_page+0x40/0x40 >> > > >> [] pagefault_out_of_memory+0x13/0x130 >> > > >> [] mm_fault_error+0x9e/0x150 >> > > >> [] do_page_fault+0x404/0x490 >> > > >> [] ? do_mmap_pgoff+0x3dc/0x430 >> > > >> [] page_fault+0x1f/0x30 >> > > > >> > > >This is a regular memcg OOM killer. Which dumps messages about what is >> > > >going to do. So no, nothing unusual, except if it was like that for ever >> > > >which would mean that oom_kill_process is in the endless loop. But a >> > > >single stack doesn't tell us much. >> > > > >> > > >Just a note. When you see something hogging a cpu and you are not sure >> > > >whether it might be in an endless loop inside the kernel it makes sense >> > > >to take several snaphosts of the stack trace and see if it changes. If >> > > >not and the process is not sleeping (there is no schedule on the trace) >> > > >then it might be looping somewhere waiting for Godot. If it is sleeping >> > > >then it is slightly harder because you would have to identify what it is >> > > >waiting for which requires to know a deeper context. >> > > >-- >> > > >Michal Hocko >> > > >SUSE Labs >> > > >> > > >> > > >> > > I was finally able to get stack of problematic process :) I saved it two times from the same process, as Michal suggested (i wasn't able to take more). Here it is: >> > > >> > > First (doesn't look very helpfull): >> > > [] 0xffffffffffffffff >> > > >> > > >> > > Second: >> > > [] shrink_zone+0x481/0x650 >> > > [] do_try_to_free_pages+0xde/0x550 >> > > [] try_to_free_pages+0x9b/0x120 >> > > [] free_more_memory+0x5d/0x60 >> > > [] __getblk+0x14d/0x2c0 >> > > [] __bread+0x13/0xc0 >> > > [] ext3_get_branch+0x98/0x140 >> > > [] ext3_get_blocks_handle+0xd7/0xdc0 >> > > [] ext3_get_block+0xc4/0x120 >> > > [] do_mpage_readpage+0x38a/0x690 >> > > [] mpage_readpages+0xfb/0x160 >> > > [] ext3_readpages+0x1d/0x20 >> > > [] __do_page_cache_readahead+0x1c5/0x270 >> > > [] ra_submit+0x21/0x30 >> > > [] filemap_fault+0x380/0x4f0 >> > > [] __do_fault+0x78/0x5a0 >> > > [] handle_pte_fault+0x84/0x940 >> > > [] handle_mm_fault+0x16a/0x320 >> > > [] do_page_fault+0x13b/0x490 >> > > [] page_fault+0x1f/0x30 >> > > [] 0xffffffffffffffff >> > >> > Ah, crap. I'm sorry. You even showed us this exact trace before in >> > another context, but I did not fully realize what __getblk() is doing. >> > >> > My subsequent patches made a charge attempt return -ENOMEM without >> > reclaim if the memcg is under OOM. And so the reason you have these >> > reclaim livelocks is because __getblk never fails on -ENOMEM. When >> > the allocation returns -ENOMEM, it invokes GLOBAL DIRECT RECLAIM and >> > tries again in an endless loop. The memcg code would previously just >> > loop inside the charge, reclaiming and killing, until the allocation >> > succeeded. But the new code relies on the fault stack being unwound >> > to complete the OOM kill. And since the stack is not unwound with >> > __getblk() looping around the allocation there is no more memcg >> > reclaim AND no memcg OOM kill, thus no chance of exiting. >> > >> > That code is weird but really old, so it may take a while to evaluate >> > all the callers as to whether this can be changed. >> > >> > In the meantime, I would just allow __getblk to bypass the memcg limit >> > when it still can't charge after reclaim. Does the below get your >> > machine back on track? >> >> Scratch that. The idea is reasonable but the implementation is not >> fully cooked yet. I'll send you an update. > >Here is an update. Full replacement on top of 3.2 since we tried a >dead end and it would be more painful to revert individual changes. > >The first bug you had was the same task entering OOM repeatedly and >leaking the memcg reference, thus creating undeletable memcgs. My >fixup added a condition that if the task already set up an OOM context >in that fault, another charge attempt would immediately return -ENOMEM >without even trying reclaim anymore. This dropped __getblk() into an >endless loop of waking the flushers and performing global reclaim and >memcg returning -ENOMEM regardless of free memory. > >The update now basically only changes this -ENOMEM to bypass, so that >the memory is not accounted and the limit ignored. OOM killed tasks >are granted the same right, so that they can exit quickly and release >memory. Likewise, we want a task that hit the OOM condition also to >finish the fault quickly so that it can invoke the OOM killer. > >Does the following work for you, azur? Compiled fine, I wil install new kernel this night. Thank you! azur -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/