From: Phil Turmel <philip@turmel.org>
To: Dallas Clement <dallas.a.clement@gmail.com>
Cc: "linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>
Subject: Re: RAID 5,6 sequential writing seems slower in newer kernels
Date: Wed, 2 Dec 2015 23:30:00 -0500 [thread overview]
Message-ID: <565FC548.1060302@turmel.org> (raw)
In-Reply-To: <CAE9DZUQhwXYOA1mMOQX4UjPCBiRJuVKRf1woVmuW1RWO4WzL5Q@mail.gmail.com>
On 12/02/2015 09:51 PM, Dallas Clement wrote:
> On Wed, Dec 2, 2015 at 8:38 PM, Phil Turmel <philip@turmel.org> wrote:
>> On 12/02/2015 09:33 PM, Dallas Clement wrote:
>>
>>> I'm not sure that the sync=1 has any effect in this case where I've
>>> got direct=1 set (for non buffered I/O). I think the sync=1 flag only
>>> matters for buffered I/O. I really shouldn't be setting that flag at
>>> all.
>>
>> It's substantially different from direct=1. O_DIRECT just bypasses the
>> kernel's caches. O_SYNC flushes the file data and filesystem metadata,
>> and kills the device caches and queues.
>
> Isn't O_SYNC only applicable for buffered I/O or going through the
> kernel caches? If I'm using O_DIRECT, seems like it should just
> ignore this flag.
O_SYNC is orthogonal to whether the kernel caches are involved. It is
about ensuring that data *and* metadata are safely written all the way
to permanent media.
Phil
next prev parent reply other threads:[~2015-12-03 4:30 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-01 23:02 RAID 5,6 sequential writing seems slower in newer kernels Dallas Clement
2015-12-02 1:07 ` keld
2015-12-02 14:18 ` Robert Kierski
2015-12-02 14:45 ` Phil Turmel
2015-12-02 15:28 ` Robert Kierski
2015-12-02 15:37 ` Phil Turmel
2015-12-02 15:44 ` Robert Kierski
2015-12-02 15:51 ` Phil Turmel
2015-12-02 19:50 ` Dallas Clement
2015-12-03 0:12 ` Dallas Clement
2015-12-03 2:18 ` Phil Turmel
2015-12-03 2:24 ` Dallas Clement
2015-12-03 2:33 ` Dallas Clement
2015-12-03 2:38 ` Phil Turmel
2015-12-03 2:51 ` Dallas Clement
2015-12-03 4:30 ` Phil Turmel [this message]
2015-12-03 4:49 ` Dallas Clement
2015-12-03 13:43 ` Robert Kierski
2015-12-03 14:37 ` Phil Turmel
2015-12-03 2:34 ` Phil Turmel
2015-12-03 14:19 ` Robert Kierski
2015-12-03 14:39 ` Dallas Clement
2015-12-03 15:04 ` Phil Turmel
2015-12-03 22:21 ` Weedy
2015-12-04 13:40 ` Robert Kierski
2015-12-04 16:08 ` Dallas Clement
2015-12-07 14:29 ` Robert Kierski
2015-12-08 19:38 ` Dallas Clement
2015-12-08 21:24 ` Robert Kierski
2015-12-04 18:51 ` Shaohua Li
2015-12-05 1:38 ` Dallas Clement
2015-12-07 14:18 ` Robert Kierski
2015-12-02 15:37 ` Robert Kierski
2015-12-02 5:22 ` Roman Mamedov
2015-12-02 14:15 ` Robert Kierski
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