Date: Thu, 18 Mar 2004 20:47:46 +0100
From: Jens Axboe <axboe@suse.de>
To: Peter Zaitsev <peter@mysql.com>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: True  fsync() in Linux (on IDE)
Message-ID: <20040318194745.GA2314@suse.de>
References: <1079572101.2748.711.camel@abyss.local> <20040318064757.GA1072@suse.de> <1079639060.3102.282.camel@abyss.local>
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On Thu, Mar 18 2004, Peter Zaitsev wrote:
> On Wed, 2004-03-17 at 22:47, Jens Axboe wrote:
> 
> > > There is solution just to disable drive write cache, but it seems to
> > > slowdown performance way to much.
> > 
> > Chris and I have working real fsync() with the barrier patches. I'll
> > clean it up and post a patch for vanilla 2.6.5-rc today.
> 
> Good to hear. How is it going to work from user point of view ? 
> Just fsync working back again or there would be some special handling.

It's just going to work :)

> Also. What is about  fsync() in 2.6 nowadays ?
> 
> I've done some tests on 3WARE RAID array and it looks like  it is
> different compared to 2.4 I've been testing previously. 
> 
> I have the simple test which has single page writes to the file followed
> by fsync().   First run give you the case when file grows with each
> write, second when you're writing to existing file space.
> 
> The results I have on 2.4 is something like  40 sec per 1000 fsyncs for 
> new file, and 0.6 sec for existing file.
> 
> With 2.6.3 I have  both existing file and new file to complete in less
> than 1 second. 

I believe some missed set_page_writeback() calls caused fsync() to never
really wait on anything, pretty broken... IIRC, it's fixed in latest
-mm, or maybe it's just pending for next release.

-- 
Jens Axboe

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