linux-kernel - Re: [PATCH] Optimize struct task_delay

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Date:	Mon, 23 Jul 2007 09:08:34 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	Shailabh Nagar <nagar1234@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Optimize struct task_delay_info

On Wed, 2007-07-18 at 12:30 +0800, Zhang, Yanmin wrote:
> On Wed, 2007-07-11 at 17:16 +0530, Balbir Singh wrote:
> > Zhang, Yanmin wrote:
> > > struct task_delay_info is used by per process block I/O delay statistics
> > > feature which is useful in kernel. This struct is not optimized.
> > > 
> > > My patch against kernel 2.6.22 shrinks it a half.
> > > 
> > > 1) Delete blkio_start and blkio_end. As the collection happens in
> > > io_schedule and io_schedule_timeout, we use local variables to
> > > replace them;
> > > 2) Delete lock. The change to the protected data has no nested cases.
> > > In addition, the result is for performance data collection, so it’s
> > > unnecessary to add such lock. 
> > > 3) Delete flags. It just has one value. Use the most significant bit of
> > > blkio_delay (64 bits) to mark it..
> > > 
> > > 
> > > Signed-off-by: Zhang Yanmin <yanmin.zhang@...el.com>
> > 
> > Hi, Yanmin,
> > 
> > Did you see any particular performance issues with the delay accounting
> > patches? Is the patch tested; could you please provide test results?
> It's hard to find an appropriate benchmark to test it. Anyway, I used sysbench
> to test it on my x86_64 machine. My machine has 16 logical cpu, dual-core+hyperThread.
> memory is 8GB and disk is one SATA.
> 
> I tested both sequence and rand.
> 1) seq read/write:use command line:
> echo "3">/proc/sys/vm/drop_caches; sysbench --test=fileio --file-test-mode=seqrewr
> --num-threads=32 --file-total-size=1500M --max-requests=150000 --max-time=3000 run;
> 
> Run the command for 20 times and get average result:
> Without patch: 49.7511Mb/sec
> With patch: 51.6557Mb/sec
> Improvement: 3.8%
> 
> 
> 2) Rand read/write:use command line:
> echo "3">/proc/sys/vm/drop_caches; sysbench --test=fileio --file-test-mode=rndrw
> --num-threads=32 --file-total-size=800M --max-requests=15000 --max-time=3000 run;
> 
> Run the command for 10 times and get average result:
> Without patch: 7.25657Mb/sec
> With patch: 7.35052Mb/sec
> Improvement: 1.3%
> 
> 
> I didn't use application to read the delay accounting info. If I did, I guess the improvement
> is better.
> 
> > 
> > Meanwhile, I'll review these patches and I am correcting Shailabh's id
> > to his new email id.
Man,

What's your comment about the patch?

Thanks,
Yanmin
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