Date: Wed, 16 Nov 2005 18:38:09 +0000
From: Christoph Hellwig <hch@infradead.org>
To: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Andrew Morton <akpm@osdl.org>, theonetruekenny@yahoo.com,
       linux-kernel@vger.kernel.org
Subject: Re: mmap over nfs leads to excessive system load
Message-ID: <20051116183808.GA5642@infradead.org>
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	Trond Myklebust <trond.myklebust@fys.uio.no>,
	Andrew Morton <akpm@osdl.org>, theonetruekenny@yahoo.com,
	linux-kernel@vger.kernel.org
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On Wed, Nov 16, 2005 at 01:34:22PM -0500, Trond Myklebust wrote:
> Not really. The pages aren't flushed at this time. We the point is to
> gather several pages and coalesce them into one over-the-wire RPC call.
> That means we cannot really do it from inside ->writepage().
> 
> We do start the actual RPC calls in ->writepages(), though.

This is a problem we have in various filesystems.  Except for really
bad OOM situations the filesystem should never get a writeout request
for a single file.  We should really stop having ->writepage called by
the VM and move this kind of batching code into the VM.  I'm runnin into
similar issues for XFS and unwritten/delayed extent conversion once again.

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