From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx171.postini.com [74.125.245.171]) by kanga.kvack.org (Postfix) with SMTP id 983666B004D for ; Fri, 6 Jan 2012 01:33:08 -0500 (EST) Received: by qadc16 with SMTP id c16so916846qad.14 for ; Thu, 05 Jan 2012 22:33:07 -0800 (PST) Message-ID: <4F06959D.2070100@gmail.com> Date: Fri, 06 Jan 2012 01:33:01 -0500 From: KOSAKI Motohiro 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> <4F06951E.7050605@tao.ma> In-Reply-To: <4F06951E.7050605@tao.ma> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tao Ma Cc: KOSAKI Motohiro , linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Rientjes , Minchan Kim , Mel Gorman , Johannes Weiner , Andrew Morton (1/6/12 1:30 AM), Tao Ma wrote: > 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? read whole thread. -- 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