linux-ext4 - Re: [PATCH 2/2] writeback: skip useless data integrity tricks for sync

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Date:	Fri, 8 Oct 2010 13:09:31 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Dmitry Monakhov <dmonakhov@...il.com>
Cc:	jaxboe@...ionio.com, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] writeback: skip useless data integrity tricks for
 sync_filesystem

On Fri, Oct 08, 2010 at 07:00:27PM +0400, Dmitry Monakhov wrote:
> If we about to write many inodes at the time, even in for
> data integrity sync, it is reasonable to skip data integrity
> logic for each inode, but perform all necessary steps at the end.
> 
> The frozen sync() issue:
> If we try to call sync() then other process dirties inodes in
> parallels we end up with writing inodes in sync mode, which
> usually result in io_barriers spam. Which result in almost 100 times
> performance degradation.

Please don't add even more flags for that.  The only ->write_inode
call that actually needs this is the one from nfsd, and filesystems
can just implement the commit_metadata inode operation to force
out transactions there.  That's what we've been doing in XFS for
a while now.

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