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 138C56B004F for ; Fri, 4 Sep 2009 01:19:15 -0400 (EDT) Date: Fri, 4 Sep 2009 14:11:57 +0900 From: Daisuke Nishimura Subject: Re: [mmotm][experimental][PATCH] coalescing charge Message-Id: <20090904141157.4640ec1e.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090904131835.ac2b8cc8.kamezawa.hiroyu@jp.fujitsu.com> References: <20090902093438.eed47a57.kamezawa.hiroyu@jp.fujitsu.com> <20090902134114.b6f1a04d.kamezawa.hiroyu@jp.fujitsu.com> <20090902182923.c6d98fd6.kamezawa.hiroyu@jp.fujitsu.com> <20090903141727.ccde7e91.nishimura@mxp.nes.nec.co.jp> <20090904131835.ac2b8cc8.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: nishimura@mxp.nes.nec.co.jp, "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "balbir@linux.vnet.ibm.com" , "akpm@linux-foundation.org" List-ID: A few more comments. On Fri, 4 Sep 2009 13:18:35 +0900, KAMEZAWA Hiroyuki wrote: > On Thu, 3 Sep 2009 14:17:27 +0900 > Daisuke Nishimura wrote: > > > = > > > This is a code for batched charging using percpu cache. > > > At charge, memcg charges 64pages and remember it in percpu cache. > > > Because it's cache, drain/flushed if necessary. > > > > > > This version uses public percpu area , not per-memcg percpu area. > > > 2 benefits of public percpu area. > > > 1. Sum of stocked charge in the system is limited to # of cpus > > > not to the number of memcg. This shows better synchonization. > > > 2. drain code for flush/cpuhotplug is very easy (and quick) > > > > > > The most important point of this patch is that we never touch res_counter > > > in fast path. The res_counter is system-wide shared counter which is modified > > > very frequently. We shouldn't touch it as far as we can for avoid false sharing. > > > > > > Signed-off-by: KAMEZAWA Hiroyuki > > It looks basically good. I'll do some tests with all patches applied. > > > thanks. > it seems that these patches make rmdir stall again... This batched charge patch seems not to be the (only) suspect, though. > > > @@ -1288,23 +1364,25 @@ static int __mem_cgroup_try_charge(struc > > > return 0; > > > > > > VM_BUG_ON(css_is_removed(&mem->css)); > > > + if (mem_cgroup_is_root(mem)) > > > + goto done; > > > + if (consume_stock(mem)) > > > + goto charged; > > > IMHO, it would be better to check consume_stock() every time in the while loop below, because someone might have already refilled the stock while the current context sleeps in reclaiming memory. > > > while (1) { > > > int ret = 0; > > > unsigned long flags = 0; > > > > > > - if (mem_cgroup_is_root(mem)) > > > - goto done; > > > - ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res); > > > + ret = res_counter_charge(&mem->res, CHARGE_SIZE, &fail_res); > > > if (likely(!ret)) { > > > if (!do_swap_account) > > > break; > > > - ret = res_counter_charge(&mem->memsw, PAGE_SIZE, > > > + ret = res_counter_charge(&mem->memsw, CHARGE_SIZE, > > > &fail_res); > > > if (likely(!ret)) > > > break; > > > /* mem+swap counter fails */ > > > - res_counter_uncharge(&mem->res, PAGE_SIZE); > > > + res_counter_uncharge(&mem->res, CHARGE_SIZE); > > > flags |= MEM_CGROUP_RECLAIM_NOSWAP; > > > mem_over_limit = mem_cgroup_from_res_counter(fail_res, > > > memsw); How about changing pre-charge size according to the loop count ? IMHO, it would be better to disable pre-charge at least in nr_retries==0 case, i.e. it is about to causing oom. P.S. I will not be so active next week. Thanks, Daisuke Nishimura. -- 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