From: Dave Chinner <david@fromorbit.com>
To: Fengguang Wu <fengguang.wu@intel.com>
Cc: Glauber Costa <glommer@parallels.com>,
Linux Memory Management List <linux-mm@kvack.org>,
linux-fsdevel@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>,
lkp@linux.intel.com
Subject: Re: [numa shrinker] 9b17c62382: -36.6% regression on sparse file copy
Date: Wed, 15 Jan 2014 11:18:27 +1100 [thread overview]
Message-ID: <20140115001827.GO3469@dastard> (raw)
In-Reply-To: <20140109025715.GA11984@localhost>
On Thu, Jan 09, 2014 at 10:57:15AM +0800, Fengguang Wu wrote:
> Hi Dave,
>
> As you suggested, I added tests for ext4 and btrfs, the results are
> the same.
>
> Then I tried running perf record for 10 seconds starting from 200s.
> (The test runs for 410s). I see several warning messages and hope
> they do not impact the accuracy too much:
>
> [ 252.608069] perf samples too long (2532 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
> [ 252.608863] perf samples too long (2507 > 2500), lowering kernel.perf_event_max_sample_rate to 25000
> [ 252.609422] INFO: NMI handler (perf_event_nmi_handler) took too long to run: 1.389 msecs
>
> Anyway the noticeable perf change are:
>
> 1d3d4437eae1bb2 9b17c62382dd2e7507984b989
> --------------- -------------------------
> 12.15 ~10% +209.8% 37.63 ~ 2% brickland2/debug2/vm-scalability/300s-btrfs-lru-file-readtwice
> 12.88 ~16% +189.4% 37.27 ~ 0% brickland2/debug2/vm-scalability/300s-ext4-lru-file-readtwice
> 15.24 ~ 9% +146.0% 37.50 ~ 1% brickland2/debug2/vm-scalability/300s-xfs-lru-file-readtwice
> 40.27 +179.1% 112.40 TOTAL perf-profile.cpu-cycles._raw_spin_lock.grab_super_passive.super_cache_count.shrink_slab.do_try_to_free_pages
>
> 1d3d4437eae1bb2 9b17c62382dd2e7507984b989
> --------------- -------------------------
> 11.91 ~12% +218.2% 37.89 ~ 2% brickland2/debug2/vm-scalability/300s-btrfs-lru-file-readtwice
> 12.47 ~16% +200.3% 37.44 ~ 0% brickland2/debug2/vm-scalability/300s-ext4-lru-file-readtwice
> 15.36 ~11% +145.4% 37.68 ~ 1% brickland2/debug2/vm-scalability/300s-xfs-lru-file-readtwice
> 39.73 +184.5% 113.01 TOTAL perf-profile.cpu-cycles._raw_spin_lock.put_super.drop_super.super_cache_count.shrink_slab
>
> perf report for 9b17c62382dd2e7507984b989:
>
> # Overhead Command Shared Object Symbol
> # ........ ............... .................. ..............................................
> #
> 77.74% dd [kernel.kallsyms] [k] _raw_spin_lock
> |
> --- _raw_spin_lock
> |
> |--47.65%-- grab_super_passive
Oh, it's superblock lock contention, probably caused by an increase
in shrinker calls (i.e. per-node rather than global). I think we've
seen this before - can you try the two patches from Tim Chen here:
https://lkml.org/lkml/2013/9/6/353
https://lkml.org/lkml/2013/9/6/356
If they fix the problem, I'll get them into 3.14 and pushed back to
the relevant stable kernels.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2014-01-15 0:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-06 8:20 [numa shrinker] 9b17c62382: -36.6% regression on sparse file copy fengguang.wu
2014-01-06 13:10 ` Dave Chinner
2014-01-08 11:14 ` Fengguang Wu
2014-01-09 2:57 ` Fengguang Wu
2014-01-15 0:18 ` Dave Chinner [this message]
2014-01-27 12:09 ` Fengguang Wu
2014-01-28 19:03 ` Tim Chen
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