From: "changtao381" <changtao381@163.com>
To: Piotr.Dalek@ts.fujitsu.com, haomaiwang@gmail.com,
ceph-devel@vger.kernel.org
Subject: 答复: journal alignment
Date: Fri, 20 Nov 2015 17:12:25 +0800 [thread overview]
Message-ID: <023e01d12373$941f1050$bc5d30f0$@com> (raw)
In-Reply-To: <d742f6275e1645cdb02b0bad23110eec@R01UKEXCASM115.r01.fujitsu.local>
Hi All,
Thanks for you apply!
If directioIO + async IO requirement that alignment, it shouldn't aligned by PAGE for each journal entry.
For it may write many entries of journal once time
So it should do alignment after [prepare_multi_write] rather than do it each in [prepare_single_write] ? Am I right?
-----邮件原件-----
发件人: Piotr.Dalek@ts.fujitsu.com [mailto:Piotr.Dalek@ts.fujitsu.com]
发送时间: 2015年11月20日 16:42
收件人: changtao381; ceph-devel@vger.kernel.org
主题: RE: journal alignment
> -----Original Message-----
> From: ceph-devel-owner@vger.kernel.org [mailto:ceph-devel-
> owner@vger.kernel.org] On Behalf Of changtao381
> Sent: Friday, November 20, 2015 9:33 AM
>
> HI All,
>
> Why it is needed an entry of journal t is aligned by CEPH_PAGE_MASK ? For
> it causes the data of journal write are amplified by 2X for small io
>
> For example write io size 4096 bytes, it may write 8192 bytes
>
> prepare_single_write 2 will write 98304 : seq 24 len 4324 -> 8192 (head 40
> pre_pad 0 ebl 4324 post_pad 3788 tail 40) (ebl alignment -1)
>
> Thanks!
It is a direct-IO+async IO requirement (writing on page-size boundary which is incidentally also a multiply of sector size).
With best regards / Pozdrawiam
Piotr Dałek
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next prev parent reply other threads:[~2015-11-20 9:12 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-20 8:33 journal alignment changtao381
2015-11-20 8:41 ` Haomai Wang
2015-11-20 8:42 ` Piotr.Dalek
2015-11-20 9:12 ` changtao381 [this message]
2015-11-20 9:16 ` 答复: " 池信泽
2015-11-20 9:19 ` 池信泽
[not found] ` <alpine.DEB.2.00.1511200339470.25088@cobra.newdream.net>
2015-11-20 13:03 ` Haomai Wang
[not found] ` <alpine.DEB.2.00.1511200507120.24879@cobra.newdream.net>
2015-11-20 13:29 ` Haomai Wang
2015-11-20 19:53 ` Evgeniy Firsov
2015-11-23 16:59 ` Haomai Wang
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