From: James Bottomley <James.Bottomley@suse.de> To: Mel Gorman <mgorman@suse.de> Cc: Jan Kara <jack@suse.cz>, colin.king@canonical.com, Chris Mason <chris.mason@oracle.com>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, linux-kernel <linux-kernel@vger.kernel.org>, linux-ext4 <linux-ext4@vger.kernel.org>, mgorman@novell.com Subject: Re: [BUG] fatal hang untarring 90GB file, possibly writeback related. Date: Thu, 28 Apr 2011 13:30:36 -0500 [thread overview] Message-ID: <1304015436.2598.19.camel@mulgrave.site> (raw) In-Reply-To: <20110428171826.GZ4658@suse.de> On Thu, 2011-04-28 at 18:18 +0100, Mel Gorman wrote: > On Thu, Apr 28, 2011 at 11:56:17AM -0500, James Bottomley wrote: > > # Events: 6K cycles > > # > > # Overhead Command Shared Object Symbol > > # ........ ........... ................... ....................................... > > # > > 20.41% kswapd0 [kernel.kallsyms] [k] shrink_slab > > | > > --- shrink_slab > > | > > |--99.91%-- kswapd > > | kthread > > | kernel_thread_helper > > --0.09%-- [...] > > > > Ok. I can't see how the patch "mm: vmscan: reclaim order-0 and use > compaction instead of lumpy reclaim" is related unless we are seeing > two problems that happen to manifest in a similar manner. > > However, there were a number of changes made to dcache in particular > for 2.6.38. Specifically thinks like dentry_kill use trylock and is > happy to loop around if it fails to acquire anything. See things like > this for example; OK, so for this, I tried a 2.6.37 kernel. It doesn't work very well, networking is hosed for no reason I can see (probably systemd / cgroups problems). However, it runs enough for me to say that the tar proceeds to completion in a non-PREEMPT kernel. (I tried several times for good measure). That makes this definitely a regression of some sort, but it doesn't definitively identify the dcache code ... it could be an ext4 bug that got introduced in 2.6.38 either. > static void try_prune_one_dentry(struct dentry *dentry) > __releases(dentry->d_lock) > { > struct dentry *parent; > > parent = dentry_kill(dentry, 0); > /* > * If dentry_kill returns NULL, we have nothing more to do. > * if it returns the same dentry, trylocks failed. In either > * case, just loop again. > > > If this in combination with many inodes being locked for whatever > reason (writeback locking them maybe?) is causing the shrinker to > return after zero progress, it could in turn cause kswapd to enter > into a loop for longish periods of time in shrink_slab here; > > while (total_scan >= SHRINK_BATCH) { > long this_scan = SHRINK_BATCH; > int shrink_ret; > int nr_before; > > nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask); > shrink_ret = (*shrinker->shrink)(shrinker, this_scan, > gfp_mask); > if (shrink_ret == -1) > break; > if (shrink_ret < nr_before) > ret += nr_before - shrink_ret; > count_vm_events(SLABS_SCANNED, this_scan); > total_scan -= this_scan; > > cond_resched(); > } > > That would explain this trace. > > > 9.98% kswapd0 [kernel.kallsyms] [k] shrink_zone > > | > > --- shrink_zone > > | > > |--99.46%-- kswapd > > | kthread > > | kernel_thread_helper > > | > > --0.54%-- kthread > > kernel_thread_helper > > > > 7.70% kswapd0 [kernel.kallsyms] [k] kswapd > > | > > --- kswapd > > kthread > > kernel_thread_helper > > > > 5.40% kswapd0 [kernel.kallsyms] [k] zone_watermark_ok_safe > > | > > --- zone_watermark_ok_safe > > | > > |--72.66%-- kswapd > > | kthread > > | kernel_thread_helper > > | > > |--20.88%-- sleeping_prematurely.part.12 > > | kswapd > > | kthread > > | kernel_thread_helper > > | > > --6.46%-- kthread > > kernel_thread_helper > > > > We are also spending an astonishing amount of time in > sleeping_prematurely leading me to believe we are failing to balance the > zones and are continually under the min watermark for one of the zones. > We are never going to sleep because of this check; > > if (total_scanned && (priority < DEF_PRIORITY - 2)) { > if (has_under_min_watermark_zone) > count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); > else > congestion_wait(BLK_RW_ASYNC, HZ/10); > } > > However, I think this is a secondary effect to the failure of shrinkers > to do their work. If slabs were being shrunk, one would expect us to > be getting over the min watermark. > > > 4.25% kswapd0 [kernel.kallsyms] [k] do_raw_spin_lock > > | > > --- do_raw_spin_lock > > | > > |--77.49%-- _raw_spin_lock > > | | > > | |--51.85%-- mb_cache_shrink_fn > > | | shrink_slab > > | | kswapd > > | | kthread > > | | kernel_thread_helper > > | | > > | --48.15%-- mem_cgroup_soft_limit_reclaim > > | kswapd > > | kthread > > | kernel_thread_helper > > | > > Way hey, cgroups are also in the mix. How jolly. > > Is systemd a common element of the machines hitting this bug by any > chance? Well, yes, the bug report is against FC15, which needs cgroups for systemd. > The remaining traces seem to be follow-on damage related to the three > issues of "shrinkers are bust in some manner" causing "we are not > getting over the min watermark" and as a side-show "we are spending lots > of time doing something unspecified but unhelpful in cgroups". Heh, well find a way for me to verify this: I can't turn off cgroups because systemd then won't work and the machine won't boot ... James
WARNING: multiple messages have this Message-ID (diff)
From: James Bottomley <James.Bottomley@suse.de> To: Mel Gorman <mgorman@suse.de> Cc: Jan Kara <jack@suse.cz>, colin.king@canonical.com, Chris Mason <chris.mason@oracle.com>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, linux-kernel <linux-kernel@vger.kernel.org>, linux-ext4 <linux-ext4@vger.kernel.org>, mgorman@novell.com Subject: Re: [BUG] fatal hang untarring 90GB file, possibly writeback related. Date: Thu, 28 Apr 2011 13:30:36 -0500 [thread overview] Message-ID: <1304015436.2598.19.camel@mulgrave.site> (raw) In-Reply-To: <20110428171826.GZ4658@suse.de> On Thu, 2011-04-28 at 18:18 +0100, Mel Gorman wrote: > On Thu, Apr 28, 2011 at 11:56:17AM -0500, James Bottomley wrote: > > # Events: 6K cycles > > # > > # Overhead Command Shared Object Symbol > > # ........ ........... ................... ....................................... > > # > > 20.41% kswapd0 [kernel.kallsyms] [k] shrink_slab > > | > > --- shrink_slab > > | > > |--99.91%-- kswapd > > | kthread > > | kernel_thread_helper > > --0.09%-- [...] > > > > Ok. I can't see how the patch "mm: vmscan: reclaim order-0 and use > compaction instead of lumpy reclaim" is related unless we are seeing > two problems that happen to manifest in a similar manner. > > However, there were a number of changes made to dcache in particular > for 2.6.38. Specifically thinks like dentry_kill use trylock and is > happy to loop around if it fails to acquire anything. See things like > this for example; OK, so for this, I tried a 2.6.37 kernel. It doesn't work very well, networking is hosed for no reason I can see (probably systemd / cgroups problems). However, it runs enough for me to say that the tar proceeds to completion in a non-PREEMPT kernel. (I tried several times for good measure). That makes this definitely a regression of some sort, but it doesn't definitively identify the dcache code ... it could be an ext4 bug that got introduced in 2.6.38 either. > static void try_prune_one_dentry(struct dentry *dentry) > __releases(dentry->d_lock) > { > struct dentry *parent; > > parent = dentry_kill(dentry, 0); > /* > * If dentry_kill returns NULL, we have nothing more to do. > * if it returns the same dentry, trylocks failed. In either > * case, just loop again. > > > If this in combination with many inodes being locked for whatever > reason (writeback locking them maybe?) is causing the shrinker to > return after zero progress, it could in turn cause kswapd to enter > into a loop for longish periods of time in shrink_slab here; > > while (total_scan >= SHRINK_BATCH) { > long this_scan = SHRINK_BATCH; > int shrink_ret; > int nr_before; > > nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask); > shrink_ret = (*shrinker->shrink)(shrinker, this_scan, > gfp_mask); > if (shrink_ret == -1) > break; > if (shrink_ret < nr_before) > ret += nr_before - shrink_ret; > count_vm_events(SLABS_SCANNED, this_scan); > total_scan -= this_scan; > > cond_resched(); > } > > That would explain this trace. > > > 9.98% kswapd0 [kernel.kallsyms] [k] shrink_zone > > | > > --- shrink_zone > > | > > |--99.46%-- kswapd > > | kthread > > | kernel_thread_helper > > | > > --0.54%-- kthread > > kernel_thread_helper > > > > 7.70% kswapd0 [kernel.kallsyms] [k] kswapd > > | > > --- kswapd > > kthread > > kernel_thread_helper > > > > 5.40% kswapd0 [kernel.kallsyms] [k] zone_watermark_ok_safe > > | > > --- zone_watermark_ok_safe > > | > > |--72.66%-- kswapd > > | kthread > > | kernel_thread_helper > > | > > |--20.88%-- sleeping_prematurely.part.12 > > | kswapd > > | kthread > > | kernel_thread_helper > > | > > --6.46%-- kthread > > kernel_thread_helper > > > > We are also spending an astonishing amount of time in > sleeping_prematurely leading me to believe we are failing to balance the > zones and are continually under the min watermark for one of the zones. > We are never going to sleep because of this check; > > if (total_scanned && (priority < DEF_PRIORITY - 2)) { > if (has_under_min_watermark_zone) > count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); > else > congestion_wait(BLK_RW_ASYNC, HZ/10); > } > > However, I think this is a secondary effect to the failure of shrinkers > to do their work. If slabs were being shrunk, one would expect us to > be getting over the min watermark. > > > 4.25% kswapd0 [kernel.kallsyms] [k] do_raw_spin_lock > > | > > --- do_raw_spin_lock > > | > > |--77.49%-- _raw_spin_lock > > | | > > | |--51.85%-- mb_cache_shrink_fn > > | | shrink_slab > > | | kswapd > > | | kthread > > | | kernel_thread_helper > > | | > > | --48.15%-- mem_cgroup_soft_limit_reclaim > > | kswapd > > | kthread > > | kernel_thread_helper > > | > > Way hey, cgroups are also in the mix. How jolly. > > Is systemd a common element of the machines hitting this bug by any > chance? Well, yes, the bug report is against FC15, which needs cgroups for systemd. > The remaining traces seem to be follow-on damage related to the three > issues of "shrinkers are bust in some manner" causing "we are not > getting over the min watermark" and as a side-show "we are spending lots > of time doing something unspecified but unhelpful in cgroups". Heh, well find a way for me to verify this: I can't turn off cgroups because systemd then won't work and the machine won't boot ... James -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-04-28 18:30 UTC|newest] Thread overview: 138+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-04-27 16:09 [BUG] fatal hang untarring 90GB file, possibly writeback related James Bottomley 2011-04-27 16:09 ` James Bottomley 2011-04-27 16:33 ` Chris Mason 2011-04-27 16:33 ` Chris Mason 2011-04-27 16:50 ` James Bottomley 2011-04-27 16:50 ` James Bottomley 2011-04-27 16:50 ` James Bottomley 2011-04-27 16:54 ` Chris Mason 2011-04-27 16:54 ` Chris Mason 2011-04-27 17:21 ` James Bottomley 2011-04-27 17:21 ` James Bottomley 2011-04-27 17:21 ` James Bottomley 2011-04-27 17:34 ` Chris Mason 2011-04-27 17:34 ` Chris Mason 2011-04-27 17:50 ` James Bottomley 2011-04-27 17:50 ` James Bottomley 2011-04-27 18:25 ` Colin Ian King 2011-04-27 18:25 ` Colin Ian King 2011-04-28 15:57 ` James Bottomley 2011-04-28 15:57 ` James Bottomley 2011-04-27 20:05 ` James Bottomley 2011-04-27 20:05 ` James Bottomley 2011-04-28 11:36 ` Colin Ian King 2011-04-28 11:36 ` Colin Ian King 2011-04-28 12:29 ` Chris Mason 2011-04-28 12:29 ` Chris Mason 2011-04-28 13:42 ` Colin Ian King 2011-04-28 13:42 ` Colin Ian King 2011-04-28 13:45 ` Chris Mason 2011-04-28 13:45 ` Chris Mason 2011-04-28 14:01 ` Colin Ian King 2011-04-28 14:04 ` Chris Mason 2011-04-28 14:04 ` Chris Mason 2011-04-28 15:23 ` Colin Ian King 2011-04-28 14:25 ` Jan Kara 2011-04-28 14:25 ` Jan Kara 2011-04-28 14:33 ` Jan Kara 2011-04-28 14:33 ` Jan Kara 2011-04-28 14:58 ` Colin Ian King 2011-04-28 22:40 ` Jan Kara 2011-04-28 22:40 ` Jan Kara 2011-04-28 22:44 ` James Bottomley 2011-04-28 22:44 ` James Bottomley 2011-05-03 18:55 ` Colin Ian King 2011-05-03 18:55 ` Colin Ian King 2011-04-28 16:11 ` James Bottomley 2011-04-28 16:11 ` James Bottomley 2011-04-28 14:49 ` James Bottomley 2011-04-28 14:49 ` James Bottomley 2011-04-28 13:52 ` Jan Kara 2011-04-28 13:52 ` Jan Kara 2011-04-28 14:07 ` Mel Gorman 2011-04-28 14:07 ` Mel Gorman 2011-04-28 14:25 ` James Bottomley 2011-04-28 14:25 ` James Bottomley 2011-04-28 15:08 ` Mel Gorman 2011-04-28 15:08 ` Mel Gorman 2011-04-28 16:01 ` James Bottomley 2011-04-28 16:01 ` James Bottomley 2011-04-28 16:50 ` James Bottomley 2011-04-28 16:50 ` James Bottomley 2011-04-28 16:56 ` James Bottomley 2011-04-28 16:56 ` James Bottomley 2011-04-28 17:18 ` Mel Gorman 2011-04-28 17:18 ` Mel Gorman 2011-04-28 18:30 ` James Bottomley [this message] 2011-04-28 18:30 ` James Bottomley 2011-04-28 19:21 ` Mel Gorman 2011-04-28 19:21 ` Mel Gorman 2011-04-28 19:59 ` James Bottomley 2011-04-28 19:59 ` James Bottomley 2011-04-28 20:27 ` Mel Gorman 2011-04-28 20:27 ` Mel Gorman 2011-04-29 15:02 ` James Bottomley 2011-04-29 15:02 ` James Bottomley 2011-04-28 21:12 ` James Bottomley 2011-04-28 21:12 ` James Bottomley 2011-04-28 22:43 ` James Bottomley 2011-04-28 22:43 ` James Bottomley 2011-05-03 9:13 ` Mel Gorman 2011-05-03 9:13 ` Mel Gorman 2011-05-03 14:13 ` James Bottomley 2011-05-03 14:13 ` James Bottomley 2011-05-03 14:22 ` James Bottomley 2011-05-06 7:42 ` Mel Gorman 2011-05-06 7:42 ` Mel Gorman 2011-05-06 8:07 ` Mel Gorman 2011-05-09 18:16 ` James Bottomley 2011-05-09 18:16 ` James Bottomley 2011-05-10 10:21 ` Mel Gorman 2011-05-10 10:21 ` Mel Gorman 2011-05-10 10:33 ` Pekka Enberg 2011-05-10 10:33 ` Pekka Enberg 2011-05-10 14:01 ` James Bottomley 2011-05-10 14:01 ` James Bottomley 2011-05-10 14:35 ` Mel Gorman 2011-05-10 14:35 ` Mel Gorman 2011-05-10 15:29 ` James Bottomley 2011-05-10 15:29 ` James Bottomley 2011-05-10 15:57 ` James Bottomley 2011-05-10 15:57 ` James Bottomley 2011-05-10 17:05 ` James Bottomley 2011-05-10 17:05 ` James Bottomley 2011-05-10 17:17 ` Mel Gorman 2011-05-10 17:17 ` Mel Gorman 2011-05-10 17:29 ` James Bottomley 2011-05-10 17:29 ` James Bottomley 2011-05-10 21:08 ` Raghavendra D Prabhu 2011-05-11 9:16 ` Mel Gorman 2011-05-11 9:16 ` Mel Gorman 2011-05-06 11:42 ` Mel Gorman 2011-05-06 11:42 ` Mel Gorman 2011-05-06 15:44 ` Mel Gorman 2011-05-06 15:44 ` Mel Gorman 2011-05-06 19:14 ` James Bottomley 2011-05-06 19:14 ` James Bottomley 2011-05-06 19:37 ` Mel Gorman 2011-05-06 19:37 ` Mel Gorman 2011-05-10 5:37 ` Colin Ian King 2011-05-10 5:37 ` Colin Ian King 2011-05-10 5:37 ` Colin Ian King 2011-05-06 15:58 ` James Bottomley 2011-05-03 9:54 ` Colin Ian King 2011-05-03 9:54 ` Colin Ian King 2011-04-28 17:10 ` Colin Ian King 2011-04-28 17:10 ` Colin Ian King 2011-04-28 0:37 ` Dave Chinner 2011-04-28 0:37 ` Dave Chinner 2011-04-29 10:23 ` Sedat Dilek 2011-04-29 10:23 ` Sedat Dilek 2011-04-29 15:37 ` James Bottomley 2011-04-29 15:37 ` James Bottomley 2011-04-29 16:31 ` James Bottomley 2011-04-29 16:31 ` James Bottomley 2011-04-29 18:02 ` James Bottomley 2011-04-29 18:02 ` James Bottomley 2011-05-02 20:04 ` James Bottomley 2011-05-02 20:04 ` James Bottomley
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