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Re: [PATCH 09/10] xfs: xfs_fs_write_inode() can fail to write inodes syn

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 09/10] xfs: xfs_fs_write_inode() can fail to write inodes synchronously V2
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 4 Feb 2010 10:02:35 +1100
Cc: bpm@xxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <20100203205648.GA23116@xxxxxxxxxxxxx>
References: <1265153104-29680-1-git-send-email-david@xxxxxxxxxxxxx> <1265153104-29680-10-git-send-email-david@xxxxxxxxxxxxx> <20100203112753.GA19996@xxxxxxxxxxxxx> <20100203205648.GA23116@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Wed, Feb 03, 2010 at 03:56:48PM -0500, Christoph Hellwig wrote:
> On Wed, Feb 03, 2010 at 06:27:53AM -0500, Christoph Hellwig wrote:
> > Still not entirely happy with this one.  The first one is that I think
> > the barriers in fsync are still too heavy for the normal sync use
> > case.  I'd be more happy with exporting the body of xfs_fsync without
> > the cache flushes (and a ebtter name than xfs_fsync) and use that
> > for write_inode.
> > 
> > That leaves open the NFSD case thought.  I'd prefer to have that fixed
> > if possibly.  Ben, any chance you could send your patch to use fsync
> > to the nfs list ASAP?  I think we'd be even better off to just force
> > -o wsync and disable ->write_inode entirely for NFS, any chance you
> > could test such a patch on your setup?
> 
> Thinking about it, we usually do cause a log buffer write from ->fsync
> which means we submit the barrier anyway.  That might be the reason
> why you're not seeing the performance hit in your testing.  With that
> I'm okay with the patch as-is for now, we can micro-optimize it later.

OK. I was thinking that a "inode cluster fsync" function might be
appropriate here. i.e. a transaction that takes all the dirty inodes
in the inode cluster and logs/forces them all in one transaction.
That would substanitally reduce the number of log writes needed,
I think. I'll look into this over the next few days.

Thanks for the reviews, Christoph.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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