linux-kernel - Re: [PATCH 4/7] zram: use atomic operation for stat

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Message-Id: <20140113162325.93896b1928f2c4a320f52d80@linux-foundation.org>
Date:	Mon, 13 Jan 2014 16:23:25 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Minchan Kim <minchan@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH 4/7] zram: use atomic operation for stat

On Tue, 14 Jan 2014 09:19:35 +0900 Minchan Kim <minchan@...nel.org> wrote:

> On Mon, Jan 13, 2014 at 03:58:14PM -0800, Andrew Morton wrote:
> > On Mon, 13 Jan 2014 20:18:59 +0900 Minchan Kim <minchan@...nel.org> wrote:
> > 
> > > Some of fields in zram->stats are protected by zram->lock which
> > > is rather coarse-grained so let's use atomic operation without
> > > explict locking.
> > 
> > Confused.  The patch didn't remove any locking, so it made the code
> > slower.
> 
> True but it could make remove dependency of zram->lock for 32bit stat
> so further patches can remove messy code and enhance write performance.
> So, it's preparing patch for further step.
> Should I rewrite the description to explain this?

That would be useful ;) I'd ask for performance testing results but I
expect they'll say "no difference".

I grabbed patches 1-3 as they seems appropriate for 3.14.

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