From: jim owens <jowens@hp.com>
To: Bryan Henderson <hbryan@us.ibm.com>
Cc: linux-fsdevel@vger.kernel.org
Subject: Re: fdatasync/barriers (was : [Bug 421482] Firefox 3 uses fsync excessively)
Date: Thu, 29 May 2008 14:46:10 -0400 [thread overview]
Message-ID: <483EF9F2.1000408@hp.com> (raw)
In-Reply-To: <OF96824E74.387F8AD7-ON88257458.005D1BC3-88257458.005E2EC4@us.ibm.com>
Bryan Henderson wrote:
>>Here's a thought for someone implementing fdatasync(). If a database
>>uses O_DIRECT writes (typically with aio), then wants data which it's
>>written to be committed to the hard disk platter, and the filesystem
>>is mounted "barrier=1" - should it call fdatasync()? Should that emit
>>the barrier? If another application uses normal (not O_DIRECT)
>>writes, and then _is delayed_ so long that kernel writeback occurs and
>>all cache is clean, and then calls fdatasync(), should that call emit
>>a barrier in that case? (Answers imho: yes and yes).
>
>
> I don't get it. What would be the value of emitting the barrier?
In both cases the FS must flush the drive write cache.
So which of Jamie's traps got you ...
EMIT (SEND) the barrier, not OMIT.
"all cache is clean": meaning KERNEL cache, not DRIVE cache.
? :) jim
next prev parent reply other threads:[~2008-05-29 18:46 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-421482-310856@https.bugzilla.mozilla.org/>
[not found] ` <200805260513.m4Q5DAU8018498@mrapp54.mozilla.org>
2008-05-26 7:05 ` [Bug 421482] Firefox 3 uses fsync excessively Andrew Morton
2008-05-26 10:07 ` Theodore Tso
2008-05-26 11:10 ` Jörn Engel
2008-05-26 11:38 ` Theodore Tso
2008-05-26 12:52 ` Jörn Engel
2008-05-26 20:22 ` Jamie Lokier
2008-05-29 17:08 ` fdatasync/barriers (was : [Bug 421482] Firefox 3 uses fsync excessively) Bryan Henderson
2008-05-29 18:46 ` jim owens [this message]
2008-05-29 23:15 ` Bryan Henderson
2008-05-30 4:00 ` Timothy Shimmin
2008-05-30 14:14 ` jim owens
2008-05-30 16:25 ` Bryan Henderson
2008-05-30 18:48 ` jim owens
2008-06-02 17:31 ` Bryan Henderson
2008-05-26 18:49 ` [Bug 421482] Firefox 3 uses fsync excessively Andrew Morton
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