linux-ext4 - Re: [Bugme-new] [Bug 9911] New: fsync blocks concurrent writes to file

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Date:	Thu, 7 Feb 2008 19:14:10 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	linux-ext4@...r.kernel.org
Cc:	bugme-daemon@...zilla.kernel.org, llowrey@...learwinter.com
Subject: Re: [Bugme-new] [Bug 9911] New: fsync blocks concurrent writes to
 file

On Thu,  7 Feb 2008 17:40:57 -0800 (PST) bugme-daemon@...zilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=9911
> 
>            Summary: fsync blocks concurrent writes to file
>            Product: File System
>            Version: 2.5
>      KernelVersion: 2.6.23.8
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: ext3
>         AssignedTo: akpm@...l.org
>         ReportedBy: llowrey@...learwinter.com
> 
> 
> Latest working kernel version: none
> Earliest failing kernel version: 2.6.18
> Distribution: RHEL 4 & Fedora 8
> Hardware Environment: Dual Xeon & dual-core Athlon
> Software Environment: Java 1.5.0_14
> Problem Description: Multiple threads append transactions to a single file.
> When fsyncs are issued, no writes complete until the fsync completes. This has
> the effect of yielding the same write rate regardless of how many threads are
> writing to the file. Solaris 10 does not exhibit this problem and scales well
> as additional threads are added.
> 
> I have confirmed this by running strace and witnessing that writes block until
> immediately after the fsync completes.
> 
> When using truss on Solaris I have witnessed multiple writes completing while
> an fsync was in progress.
> 
> Steps to reproduce:
> 
> Open a file for writing.
> Launch multiple threads with each one writing data and followed by an fsync,
> but only if data has been written since the last fsync.
> 
> 
> I have googled this issue substantially and have found no answers.
> 

I supposing teaching java about sync_file_range() would be all too hard.

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