From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx148.postini.com [74.125.245.148]) by kanga.kvack.org (Postfix) with SMTP id BCA556B004D for ; Fri, 6 Jan 2012 01:31:32 -0500 (EST) Message-ID: <4F06951E.7050605@tao.ma> Date: Fri, 06 Jan 2012 14:30:54 +0800 From: Tao Ma MIME-Version: 1.0 Subject: Re: [PATCH] mm: do not drain pagevecs for mlock References: <1325226961-4271-1-git-send-email-tm@tao.ma> <4EFD7AE3.8020403@tao.ma> <4EFD8832.6010905@tao.ma> <4F069120.8060300@tao.ma> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Rientjes , Minchan Kim , Mel Gorman , Johannes Weiner , Andrew Morton On 01/06/2012 02:18 PM, KOSAKI Motohiro wrote: > 2012/1/6 Tao Ma : >> Hi Kosaki, >> On 12/30/2011 06:07 PM, KOSAKI Motohiro wrote: >>>>> Because your test program is too artificial. 20sec/100000times = >>>>> 200usec. And your >>>>> program repeat mlock and munlock the exact same address. so, yes, if >>>>> lru_add_drain_all() is removed, it become near no-op. but it's >>>>> worthless comparision. >>>>> none of any practical program does such strange mlock usage. >>>> yes, I should say it is artificial. But mlock did cause the problem in >>>> our product system and perf shows that the mlock uses the system time >>>> much more than others. That's the reason we created this program to test >>>> whether mlock really sucks. And we compared the result with >>>> rhel5(2.6.18) which runs much much faster. >>>> >>>> And from the commit log you described, we can remove lru_add_drain_all >>>> safely here, so why add it? At least removing it makes mlock much faster >>>> compared to the vanilla kernel. >>> >>> If we remove it, we lose to a test way of mlock. "Memlocked" field of >>> /proc/meminfo >>> show inaccurate number very easily. So, if 200usec is no avoidable, >>> I'll ack you. >>> But I'm not convinced yet. >> Do you find something new for this? > > No. > > Or more exactly, 200usec is my calculation mistake. your program call mlock > 3 times per each iteration. so, correct cost is 66usec. yes, so mlock can do 15000/s, it is even slower than the whole i/o time for some not very fast ssd disk and I don't think it is endurable. I guess we should remove it, right? Or you have another other suggestion that I can try for it? Thanks Tao -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org