From: Rik van Riel <riel@redhat.com>
To: Nauman Rafique <nauman@google.com>
Cc: guijianfeng@cn.fujitsu.com, linux-kernel@vger.kernel.org,
jmoyer@redhat.com, dm-devel@redhat.com,
Vivek Goyal <vgoyal@redhat.com>,
jens.axboe@oracle.com, akpm@linux-foundation.org, agk@redhat.com,
balbir@linux.vnet.ibm.com
Subject: Re: Regarding dm-ioband tests
Date: Tue, 08 Sep 2009 12:47:33 -0400 [thread overview]
Message-ID: <4AA68AA5.10505@redhat.com> (raw)
In-Reply-To: <e98e18940909080930o40008d5dnc823db96687654af@mail.gmail.com>
Nauman Rafique wrote:
> I think this is probably the key deal breaker. dm-ioband has no
> mechanism to anticipate or idle for a reader task. Without such a
> mechanism, a proportional division scheme cannot work for tasks doing
> reads.
That is a really big issue, since most reads tend to be synchronous
(the application is waiting for the read), while many writes are not
(the application is doing something else while the data is written).
Having writes take precedence over reads will really screw over the
readers, while not benefitting the writers all that much.
--
All rights reversed.
WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: Nauman Rafique <nauman@google.com>
Cc: Vivek Goyal <vgoyal@redhat.com>, Ryo Tsuruta <ryov@valinux.co.jp>,
linux-kernel@vger.kernel.org, dm-devel@redhat.com,
jens.axboe@oracle.com, agk@redhat.com, akpm@linux-foundation.org,
guijianfeng@cn.fujitsu.com, jmoyer@redhat.com,
balbir@linux.vnet.ibm.com
Subject: Re: Regarding dm-ioband tests
Date: Tue, 08 Sep 2009 12:47:33 -0400 [thread overview]
Message-ID: <4AA68AA5.10505@redhat.com> (raw)
In-Reply-To: <e98e18940909080930o40008d5dnc823db96687654af@mail.gmail.com>
Nauman Rafique wrote:
> I think this is probably the key deal breaker. dm-ioband has no
> mechanism to anticipate or idle for a reader task. Without such a
> mechanism, a proportional division scheme cannot work for tasks doing
> reads.
That is a really big issue, since most reads tend to be synchronous
(the application is waiting for the read), while many writes are not
(the application is doing something else while the data is written).
Having writes take precedence over reads will really screw over the
readers, while not benefitting the writers all that much.
--
All rights reversed.
next prev parent reply other threads:[~2009-09-08 16:47 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-01 16:50 Regarding dm-ioband tests Vivek Goyal
2009-09-01 16:50 ` Vivek Goyal
2009-09-01 17:47 ` Vivek Goyal
2009-09-01 17:47 ` Vivek Goyal
2009-09-03 13:11 ` Vivek Goyal
2009-09-03 13:11 ` Vivek Goyal
2009-09-04 1:12 ` Ryo Tsuruta
2009-09-15 21:40 ` dm-ioband fairness in terms of sectors seems to be killing disk (Was: Re: Regarding dm-ioband tests) Vivek Goyal
2009-09-15 21:40 ` Vivek Goyal
2009-09-16 11:10 ` dm-ioband fairness in terms of sectors seems to be killing disk Ryo Tsuruta
2009-09-16 11:10 ` Ryo Tsuruta
2009-09-04 4:02 ` Regarding dm-ioband tests Ryo Tsuruta
2009-09-04 4:02 ` Ryo Tsuruta
2009-09-04 23:11 ` Vivek Goyal
2009-09-04 23:11 ` Vivek Goyal
2009-09-07 11:02 ` Ryo Tsuruta
2009-09-07 11:02 ` Ryo Tsuruta
2009-09-07 13:53 ` Rik van Riel
2009-09-07 13:53 ` Rik van Riel
2009-09-08 3:01 ` Ryo Tsuruta
2009-09-08 3:01 ` Ryo Tsuruta
2009-09-08 3:22 ` Balbir Singh
2009-09-08 3:22 ` Balbir Singh
2009-09-08 5:05 ` Ryo Tsuruta
2009-09-08 5:05 ` Ryo Tsuruta
2009-09-08 13:49 ` Vivek Goyal
2009-09-08 13:49 ` Vivek Goyal
2009-09-09 5:17 ` Ryo Tsuruta
2009-09-09 5:17 ` Ryo Tsuruta
2009-09-09 13:34 ` Vivek Goyal
2009-09-09 13:34 ` Vivek Goyal
2009-09-08 13:42 ` Vivek Goyal
2009-09-08 13:42 ` Vivek Goyal
2009-09-08 16:30 ` Nauman Rafique
2009-09-08 16:30 ` Nauman Rafique
2009-09-08 16:47 ` Rik van Riel [this message]
2009-09-08 16:47 ` Rik van Riel
2009-09-08 17:54 ` Vivek Goyal
2009-09-08 17:54 ` Vivek Goyal
2009-09-15 23:37 ` ioband: Writer starves reader even without competitors (Re: Regarding dm-ioband tests) Vivek Goyal
2009-09-15 23:37 ` Vivek Goyal
2009-09-16 12:08 ` ioband: Writer starves reader even without competitors Ryo Tsuruta
2009-09-08 17:06 ` Regarding dm-ioband tests Dhaval Giani
2009-09-09 6:05 ` Ryo Tsuruta
2009-09-09 6:05 ` Ryo Tsuruta
2009-09-09 10:51 ` Dhaval Giani
2009-09-10 7:58 ` Ryo Tsuruta
2009-09-10 7:58 ` Ryo Tsuruta
2009-09-11 9:53 ` Dhaval Giani
2009-09-15 15:12 ` Ryo Tsuruta
2009-09-15 15:12 ` Ryo Tsuruta
2009-09-15 15:19 ` Balbir Singh
2009-09-15 15:19 ` Balbir Singh
2009-09-15 15:58 ` Rik van Riel
2009-09-15 15:58 ` Rik van Riel
2009-09-15 16:21 ` Ryo Tsuruta
2009-09-15 16:21 ` Ryo Tsuruta
2009-09-09 13:57 ` Vivek Goyal
2009-09-09 13:57 ` Vivek Goyal
2009-09-10 3:06 ` Ryo Tsuruta
2009-09-09 10:01 ` Ryo Tsuruta
2009-09-09 14:31 ` Vivek Goyal
2009-09-09 14:31 ` Vivek Goyal
2009-09-10 3:45 ` Ryo Tsuruta
2009-09-10 13:25 ` Vivek Goyal
2009-09-10 13:25 ` Vivek Goyal
2009-09-08 19:24 ` Rik van Riel
2009-09-08 19:24 ` Rik van Riel
2009-09-09 0:09 ` Fabio Checconi
2009-09-09 2:06 ` Vivek Goyal
2009-09-09 2:06 ` Vivek Goyal
2009-09-09 15:41 ` Fabio Checconi
2009-09-09 17:30 ` Vivek Goyal
2009-09-09 17:30 ` Vivek Goyal
2009-09-09 19:01 ` Fabio Checconi
2009-09-09 9:24 ` Ryo Tsuruta
2009-09-09 9:24 ` Ryo Tsuruta
2009-09-16 4:45 ` ioband: Limited fairness and weak isolation between groups (Was: Re: Regarding dm-ioband tests) Vivek Goyal
2009-09-16 4:45 ` Vivek Goyal
2009-09-18 7:33 ` ioband: Limited fairness and weak isolation between groups Ryo Tsuruta
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