From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx127.postini.com [74.125.245.127]) by kanga.kvack.org (Postfix) with SMTP id 35BF46B004F for ; Fri, 6 Jan 2012 01:18:24 -0500 (EST) Received: by yenq10 with SMTP id q10so640963yen.14 for ; Thu, 05 Jan 2012 22:18:23 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <4F069120.8060300@tao.ma> References: <1325226961-4271-1-git-send-email-tm@tao.ma> <4EFD7AE3.8020403@tao.ma> <4EFD8832.6010905@tao.ma> <4F069120.8060300@tao.ma> From: KOSAKI Motohiro Date: Fri, 6 Jan 2012 01:18:02 -0500 Message-ID: Subject: Re: [PATCH] mm: do not drain pagevecs for mlock Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Tao Ma Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Rientjes , Minchan Kim , Mel Gorman , Johannes Weiner , Andrew Morton 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. -- 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