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Subject: Re: [PATCH 29/35] nfs: in-commit pages accounting and wait queue
From: Trond Myklebust <Trond.Myklebust@netapp.com>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>,
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Date: Mon, 13 Dec 2010 16:15:51 -0500
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On Mon, 2010-12-13 at 22:47 +0800, Wu Fengguang wrote:
> plain text document attachment (writeback-nfs-in-commit.patch)
> When doing 10+ concurrent dd's, I observed very bumpy commits submission
> (partly because the dd's are started at the same time, and hence reached
> 4MB to-commit pages at the same time). Basically we rely on the server
> to complete and return write/commit requests, and want both to progress
> smoothly and not consume too many pages. The write request wait queue is
> not enough as it's mainly network bounded. So add another commit request
> wait queue. Only async writes need to sleep on this queue.
> 

I'm not understanding the above reasoning. Why should we serialise
commits at the per-filesystem level (and only for non-blocking flushes
at that)?

Cheers
  Trond
-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com