From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 80F6B6B009C for ; Wed, 22 Apr 2009 02:04:45 -0400 (EDT) Date: Tue, 21 Apr 2009 23:01:47 -0700 From: Andrew Morton Subject: Re: [PATCH] memcg: remove trylock_page_cgroup Message-Id: <20090421230147.eecfe82c.akpm@linux-foundation.org> In-Reply-To: <20090422134108.f21e5bba.kamezawa.hiroyu@jp.fujitsu.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: balbir@linux.vnet.ibm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "nishimura@mxp.nes.nec.co.jp" List-ID: 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. -- 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