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

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Date:	Wed, 11 Jul 2007 17:16:22 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
CC:	Shailabh Nagar <nagar1234@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Optimize struct task_delay_info

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?

Meanwhile, I'll review these patches and I am correcting Shailabh's id
to his new email id.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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