linux-kernel - RE: [PATCH v1 0/4]mmc: enable eMMC4.41 new feature background operations and HPI

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Date:	Wed, 24 Nov 2010 16:44:13 +0800
From:	"Dong, Chuanxiao" <chuanxiao.dong@...el.com>
To:	Kyungmin Park <kmpark@...radead.org>
CC:	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"cjb@...top.org" <cjb@...top.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"Yuan, Hang" <hang.yuan@...el.com>,
	정재훈 <jh80.chung@...sung.com>
Subject: RE: [PATCH v1 0/4]mmc: enable eMMC4.41 new feature background
 operations and HPI

> 
> Basic question. Do you have any performance gain or improvement?
> In my test environment. no performance gain. Yes I know it's not for
> performance improvement.
My understanding:
If BKOPS feature is not enabled, the background operations will be started when card handles some read or write command. This will impact read/write performance. If BKOPS is enabled, driver can check whether need to do a BKOPS each time after card handled a read/write command. If need, driver can start BKOPS as soon as possible when user request is empty. This will can improve read/write performance.
So I think, anyhow background operations can improve the performance, but only can be seen when your test card need to do a background operations. If your card needn't, there will be no performance gain I think. Driver will works as normal.
BTW, the BKOPS is an operational features for eMMC4.41 card, to ensure whether the card support this feature, check ext_csd[502].
> 
> How to measure or check it has some improvement?
> Any ideas?
> 
Right now I didn't know how to do a precise measurement. Maybe keep on transferring large data for a long time with a card which enabled/or not the BKOPS feature can help to get some measurement data.

Thanks
Chuanxiao