linux-kernel - Re: [PATCH 00/10] zram: various improvements and cleanups

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Date:	Tue, 31 Aug 2010 15:37:39 -0700
From:	Greg KH <greg@...ah.com>
To:	Nitin Gupta <ngupta@...are.org>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Minchan Kim <minchan.kim@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Driver Project <devel@...uxdriverproject.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/10] zram: various improvements and cleanups

On Mon, Aug 09, 2010 at 10:56:46PM +0530, Nitin Gupta wrote:
> The zram module creates RAM based block devices named /dev/zram<id>
> (<id> = 0, 1, ...). Pages written to these disks are compressed and stored
> in memory itself.
> 
> One of the major changes done is the replacement of ioctls with sysfs
> interface. One of the advantages of this approach is we no longer depend on the
> userspace tool (rzscontrol) which was used to set various parameters and check
> statistics. Maintaining updated version of rzscontrol as changes were done to
> ioctls, statistics exported etc. was a major pain.
> 
> Another significant change is the introduction of percpu stats and compression
> buffers. Earlier, we had per-device buffers protected by a mutex. This was a
> major bottleneck on multi-core systems. With these changes, benchmarks with
> fio[1] showed a speedup of about 20% for write performance on dual-core
> system (see patch 4/10 description for details).
> 
> 
> For easier testing, a single patch against 2.6.35-git8 has been uploaded at:
> http://compcache.googlecode.com/hg/sub-projects/mainline/zram_2.6.36-rc0.patch

I applied the first 2 and last 2 of these patches and they will show up
in the linux-next tree tomorrow.  I stopped there due to Andrew's
complaints about the per-cpu variable stuff.  Please resolve this and
redo the patch set and I will be glad to apply them.

thanks,

greg k-h
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