From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 14 Jan 2008 21:56:47 -0500 From: Rik van Riel Subject: Re: [RFC][PATCH 3/5] add /dev/mem_notify device Message-ID: <20080114215647.169fd245@bree.surriel.com> In-Reply-To: <20080115110918.118B.KOSAKI.MOTOHIRO@jp.fujitsu.com> References: <20080115100029.1178.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20080115111035.d516639a.kamezawa.hiroyu@jp.fujitsu.com> <20080115110918.118B.KOSAKI.MOTOHIRO@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KOSAKI Motohiro Cc: KAMEZAWA Hiroyuki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Marcelo Tosatti , Daniel Spang , Andrew Morton List-ID: On Tue, 15 Jan 2008 11:20:56 +0900 KOSAKI Motohiro wrote: > Hi Kame > > > > + if (pressure) { > > > + nr_wakeup = max_t(int, atomic_read(&nr_watcher_task)>>4, 100); > > > + atomic_long_set(&last_mem_notify, jiffies); > > > + wake_up_locked_nr(&mem_wait, nr_wakeup); > > > + } > > What is this for ? and Why ? > > Are there too many waiters ? > > my intent is for avoid thundering herd. > 100 is heuristic value. > > and too many wakeup cause too much memory freed. > I don't want it. > > of course, if any problem happened, I will change. I agree with you. Your code looks like it could be a reasonable heuristic, but the only way to really find that out is to test the code on live systems under varying workloads. Maybe we need to wake up fewer tasks more often, maybe we are better off waking up more tasks but fewer times. Either way, at this time we simply do not know and can stick with your current code. -- All rights reversed. -- 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/ . Don't email: email@kvack.org