From: Wu Fengguang <fengguang.wu@intel.com>
To: Trond Myklebust <Trond.Myklebust@netapp.com>, linux-nfs@vger.kernel.org
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@lst.de>,
Dave Chinner <david@fromorbit.com>,
Greg Thelen <gthelen@google.com>,
Minchan Kim <minchan.kim@gmail.com>,
Vivek Goyal <vgoyal@redhat.com>,
Andrea Righi <arighi@develer.com>, linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] nfs: writeback pages wait queue
Date: Sat, 22 Oct 2011 15:34:04 +0800 [thread overview]
Message-ID: <20111022073403.GA1806@localhost> (raw)
In-Reply-To: <20111020160530.GC7054@localhost>
[-- Attachment #1: Type: text/plain, Size: 2115 bytes --]
Hi,
Aside from the big improvements in the 1G,100M,10M cases, the
thresh=1M cases show big regressions. But there is a good reason.
> 3.1.0-rc8-vanilla+ 3.1.0-rc8-nfs-wq4+
> ------------------------ ------------------------
> 21.85 +97.9% 43.23 NFS-thresh=100M/nfs-10dd-4k-32p-32768M-100M:10-X
> 51.38 +42.6% 73.26 NFS-thresh=100M/nfs-1dd-4k-32p-32768M-100M:10-X
> 28.81 +145.3% 70.68 NFS-thresh=100M/nfs-2dd-4k-32p-32768M-100M:10-X
> 13.74 +57.1% 21.59 NFS-thresh=10M/nfs-10dd-4k-32p-32768M-10M:10-X
> 29.11 -0.3% 29.02 NFS-thresh=10M/nfs-1dd-4k-32p-32768M-10M:10-X
> 16.68 +90.5% 31.78 NFS-thresh=10M/nfs-2dd-4k-32p-32768M-10M:10-X
> 48.88 +41.2% 69.01 NFS-thresh=1G/nfs-10dd-4k-32p-32768M-1024M:10-X
> 57.85 +32.7% 76.74 NFS-thresh=1G/nfs-1dd-4k-32p-32768M-1024M:10-X
> 47.13 +63.1% 76.87 NFS-thresh=1G/nfs-2dd-4k-32p-32768M-1024M:10-X
> 9.82 -33.0% 6.58 NFS-thresh=1M/nfs-10dd-4k-32p-32768M-1M:10-X
> 13.72 -18.1% 11.24 NFS-thresh=1M/nfs-1dd-4k-32p-32768M-1M:10-X
> 15.68 -65.0% 5.48 NFS-thresh=1M/nfs-2dd-4k-32p-32768M-1M:10-X
> 354.65 +45.4% 515.48 TOTAL write_bw
The regressions in the thresh=1M cases are reasonably caused by the
much reduced dirty/writeback/unstable pages.
The attached graphs for the NFS-thresh=1M/nfs-10dd cases show the
differences. The vanilla kernel (first graph) is much more permissive
to allow dirty pages to exceed the global dirty limit, while the
IO-less one applies the global dirty limit much more rigidly.
Given the 18MB vs. 3MB max dirty+writeback+unstable pages, it's not
surprising to see the better performance in the vanilla kernel. And
it does not mean anything inherently wrong in the IO-less logic.
Thanks,
Fengguang
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next prev parent reply other threads:[~2011-10-22 7:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-20 15:55 [PATCH 1/2] nfs: writeback pages wait queue Wu Fengguang
2011-10-20 15:55 ` Wu Fengguang
2011-10-20 15:56 ` [PATCH 2/2] nfs: scale writeback threshold proportional to dirty threshold Wu Fengguang
2011-10-20 15:56 ` Wu Fengguang
2011-10-20 16:05 ` [PATCH 1/2] nfs: writeback pages wait queue Wu Fengguang
2011-10-20 16:05 ` Wu Fengguang
2011-10-22 7:34 ` Wu Fengguang [this message]
2011-10-23 15:54 ` Wu Fengguang
2011-10-25 21:08 ` Wu Fengguang
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