From: Eric Dumazet <eric.dumazet@gmail.com>
To: Wu Fengguang <wfg@linux.intel.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>, Jens Axboe <axboe@kernel.dk>,
Tejun Heo <tj@kernel.org>
Subject: Re: Bad SSD performance with recent kernels
Date: Sun, 29 Jan 2012 11:03:00 +0100 [thread overview]
Message-ID: <1327831380.14602.6.camel@edumazet-laptop> (raw)
In-Reply-To: <20120129055917.GB8513@localhost>
Le dimanche 29 janvier 2012 à 13:59 +0800, Wu Fengguang a écrit :
> What's the block size? If it's < 4k, performance might be hurt.
>
> blockdev --getbsz /dev/sda
>
# blockdev --getbsz /dev/sda
4096
> > FYI, I started a bisection.
>
> Thank you! If the bisection would take much human time, it should be
> easier to collect some blktrace data on reading /dev/sda for analyzes.
>
Very strange, my bissection ended on following commit :
commit 805f6b5e1cbfedfb9b3d354013e7f4b13a79270f
Author: Tao Ma <boyu.mt@taobao.com>
Date: Fri Mar 11 20:11:59 2011 +0100
blktrace: Use rq->cmd_flags directly in blk_add_trace_rq.
This makes no sense.
hdparm uses 2MB block reads, so read_ahead (128KB) is too small for best
perf
# cat /sys/class/block/sda/queue/read_ahead_kb
128
# dd if=/dev/sda of=/dev/null bs=128k
^C
63744+0 enregistrements lus
63743+0 enregistrements écrits
8354922496 octets (8,4 GB) copiés, 39,975 s, 209 MB/s
# hdparm -t /dev/sda
/dev/sda:
Timing buffered disk reads: 510 MB in 3.00 seconds = 169.75 MB/sec
# uname -a
Linux edumazet-laptop 3.0.0-15-generic #26-Ubuntu SMP Fri Jan 20
17:23:00 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
next prev parent reply other threads:[~2012-01-29 10:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-27 6:00 Herbert Poetzl
2012-01-27 6:44 ` Eric Dumazet
2012-01-28 12:51 ` Wu Fengguang
2012-01-28 13:33 ` Eric Dumazet
2012-01-29 5:59 ` Wu Fengguang
2012-01-29 8:42 ` Herbert Poetzl
2012-01-29 9:28 ` Wu Fengguang
2012-01-29 10:03 ` Eric Dumazet [this message]
2012-01-29 11:16 ` Wu Fengguang
2012-01-29 13:13 ` Eric Dumazet
2012-01-29 15:52 ` Pádraig Brady
2012-01-29 16:10 ` Wu Fengguang
2012-01-29 20:15 ` Herbert Poetzl
2012-01-30 11:18 ` Wu Fengguang
2012-01-30 12:34 ` Eric Dumazet
2012-01-30 14:01 ` Wu Fengguang
2012-01-30 14:05 ` Wu Fengguang
2012-01-30 3:17 ` Shaohua Li
2012-01-30 5:31 ` Eric Dumazet
2012-01-30 5:45 ` Shaohua Li
2012-01-30 7:13 ` Herbert Poetzl
2012-01-30 7:22 ` Shaohua Li
2012-01-30 7:36 ` Herbert Poetzl
2012-01-30 8:12 ` Shaohua Li
2012-01-30 10:31 ` Shaohua Li
2012-01-30 14:28 ` Wu Fengguang
2012-01-30 14:51 ` Eric Dumazet
2012-01-30 22:26 ` Vivek Goyal
2012-01-31 0:14 ` Shaohua Li
2012-01-31 1:07 ` Wu Fengguang
2012-01-31 3:00 ` Shaohua Li
2012-01-31 2:17 ` Eric Dumazet
2012-01-31 8:46 ` Eric Dumazet
2012-01-31 6:36 ` Herbert Poetzl
2012-01-30 14:48 ` Wu Fengguang
2012-01-28 17:01 ` Herbert Poetzl
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