Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755325AbZDVGP1 (ORCPT ); Wed, 22 Apr 2009 02:15:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752783AbZDVGPM (ORCPT ); Wed, 22 Apr 2009 02:15:12 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:47084 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752494AbZDVGPL (ORCPT ); Wed, 22 Apr 2009 02:15:11 -0400 Date: Wed, 22 Apr 2009 15:13:37 +0900 From: KAMEZAWA Hiroyuki To: Andrew Morton Cc: balbir@linux.vnet.ibm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "nishimura@mxp.nes.nec.co.jp" Subject: Re: [PATCH] memcg: remove trylock_page_cgroup Message-Id: <20090422151337.27eecb11.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090421230147.eecfe82c.akpm@linux-foundation.org> References: <20090416120316.GG7082@balbir.in.ibm.com> <20090417091459.dac2cc39.kamezawa.hiroyu@jp.fujitsu.com> <20090417014042.GB18558@balbir.in.ibm.com> <20090417110350.3144183d.kamezawa.hiroyu@jp.fujitsu.com> <20090417034539.GD18558@balbir.in.ibm.com> <20090417124951.a8472c86.kamezawa.hiroyu@jp.fujitsu.com> <20090417045623.GA3896@balbir.in.ibm.com> <20090417141726.a69ebdcc.kamezawa.hiroyu@jp.fujitsu.com> <20090417064726.GB3896@balbir.in.ibm.com> <20090417155608.eeed1f02.kamezawa.hiroyu@jp.fujitsu.com> <20090417141837.GD3896@balbir.in.ibm.com> <20090421132551.38e9960a.akpm@linux-foundation.org> <20090422090218.6d451a08.kamezawa.hiroyu@jp.fujitsu.com> <20090422121641.eb84a07e.kamezawa.hiroyu@jp.fujitsu.com> <20090421204104.faf9fc56.akpm@linux-foundation.org> <20090422134108.f21e5bba.kamezawa.hiroyu@jp.fujitsu.com> <20090421230147.eecfe82c.akpm@linux-foundation.org> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1825 Lines: 44 On Tue, 21 Apr 2009 23:01:47 -0700 Andrew Morton wrote: > On Wed, 22 Apr 2009 13:41:08 +0900 KAMEZAWA Hiroyuki wrote: > > > > I expect that it will reliably fail if the caller is running as > > > SCHED_FIFO and the machine is single-CPU, or if we're trying to yield > > > to a SCHED_OTHER task which is pinned to this CPU, etc. The cond_resched() > > > won't work. > > > > > Hm, signal_pending() is supported now (so special user scan use alaram()) > > I used yield() before cond_resched() but I was told don't use it. > > Should I replace cond_resched() with congestion_wait(HZ/10) or some ? > > msleep(1) would be typical. That can also be used to give a > predictable number of seconds for the timeout. > > If 1 millisecond is too coarse then it's possible to sleep for much > shorter intervals if the platform implements hi-res timers. We don't > appear to have a handy interface to that (usleep, microsleep, > nanosleep, etc?). > > And an attempt to sleep for 1us will fall back to 1/HZ if the platform > doesn't implement hi-res timers, so that loop will need to be turned > into a do {} while(!timer_after(jiffies, start))) thing. Probably it > should be converted to that anyway, to be better behaved/predictable, > etc. > I'm now consdiering to make this loop _short_ and call lru_add_drain_all() when the loop finds a page is busy. (lru_add_drain_all() will sleep until the end of keventd.) And yes, checking jiffies and do sleep if it seems necessary. I'll write some RFC today. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/