linux-kernel - Re: [PATCH 1/2] zram: free meta out of init

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Date:	Wed, 28 Jan 2015 14:35:42 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Jerome Marchand <jmarchan@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Nitin Gupta <ngupta@...are.org>
Subject: Re: [PATCH 1/2] zram: free meta out of init_lock

On Wed, Jan 28, 2015 at 01:58:55PM +0900, Minchan Kim wrote:
> On Wed, Jan 28, 2015 at 01:50:28PM +0900, Sergey Senozhatsky wrote:
> > On (01/28/15 13:07), Sergey Senozhatsky wrote:
> > > On (01/28/15 12:53), Sergey Senozhatsky wrote:
> > > > > So, I want to go with srcu. Do you agree? or another suggestion?
> > > > 
> > > > yes, I think we need to take a second look on srcu approach.
> > > > 
> > > 
> > > ... or we can ask lockdep to stop false alarming us and leave it as is.
> > > I wouldn't say that ->init_lock is so hard to understand.
> > > just as an option.
> > > 
> > 
> > so... returning back to barriers performance implications.
> > 
> > x86_64, lzo, 4 comp streams, 2G zram, ext4, mount -o rw,relatime,data=ordered
> > 
> >  ./iozone -t 3 -R -r 16K -s 60M -I +Z
> > 
> >        test           base          srcu
> > "  Initial write " 1299639.75   1277621.03
> > "        Rewrite " 2139387.50   2004663.94
> > "           Read " 6193415.00   5091000.00
> > "        Re-read " 6199050.38   4814297.88
> > "   Reverse Read " 4693868.88   4367201.75
> > "    Stride read " 4470633.75   4247550.00
> > "    Random read " 5115339.50   4517352.75
> > " Mixed workload " 4340747.06   3880517.31
> > "   Random write " 1982369.75   1892456.25
> > "         Pwrite " 1352550.22   1248667.78
> > "          Pread " 2853150.06   2445154.41
> > "         Fwrite " 2367397.81   2262384.56
> > "          Fread " 8100746.50   7578071.75
> > 
> > not good.
> > 
> 
> Oops, I never thought it could make mesurable performance.
> I will investigate it.
> 
> Thanks a lot, Sergey!

Sergey, the data is consistent for repeated work?

I tested it with dd on /dev/zram0 without any FS on my KVM
and I cannot see any measureable performance gap.
Hmm, I will try it on real machine.

-- 
Kind regards,
Minchan Kim
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