Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753243AbZDVEmx (ORCPT ); Wed, 22 Apr 2009 00:42:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751501AbZDVEmn (ORCPT ); Wed, 22 Apr 2009 00:42:43 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:56316 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751240AbZDVEmm (ORCPT ); Wed, 22 Apr 2009 00:42:42 -0400 Date: Wed, 22 Apr 2009 13:41:08 +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: <20090422134108.f21e5bba.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090421204104.faf9fc56.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> 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: 3706 Lines: 97 On Tue, 21 Apr 2009 20:41:04 -0700 Andrew Morton wrote: > On Wed, 22 Apr 2009 12:16:41 +0900 KAMEZAWA Hiroyuki wrote: > > > How about this ? worth to be tested, I think. > > -Kame > > == > > From: KAMEZAWA Hiroyuki > > > > Before synchronized-LRU patch, mem cgroup had its own LRU lock. > > And there was a code which does > > # assume mz as per zone struct of memcg. > > > > spin_lock mz->lru_lock > > lock_page_cgroup(pc). > > and > > lock_page_cgroup(pc) > > spin_lock mz->lru_lock > > > > because we cannot locate "mz" until we see pc->page_cgroup, we used > > trylock(). But now, we don't have mz->lru_lock. All cgroup > > uses zone->lru_lock for handling list. Moreover, manipulation of > > LRU depends on global LRU now and we can isolate page from LRU by > > very generic way.(isolate_lru_page()). > > So, this kind of trylock is not necessary now. > > > > I thought I removed all trylock in synchronized-LRU patch but there > > is still one. This patch removes trylock used in memcontrol.c and > > its definition. If someone needs, he should add this again with enough > > reason. > > > > Signed-off-by: KAMEZAWA Hiroyuki > > --- > > include/linux/page_cgroup.h | 5 ----- > > mm/memcontrol.c | 3 +-- > > 2 files changed, 1 insertion(+), 7 deletions(-) > > > > Index: mmotm-2.6.30-Apr21/include/linux/page_cgroup.h > > =================================================================== > > --- mmotm-2.6.30-Apr21.orig/include/linux/page_cgroup.h > > +++ mmotm-2.6.30-Apr21/include/linux/page_cgroup.h > > @@ -61,11 +61,6 @@ static inline void lock_page_cgroup(stru > > bit_spin_lock(PCG_LOCK, &pc->flags); > > } > > > > -static inline int trylock_page_cgroup(struct page_cgroup *pc) > > -{ > > - return bit_spin_trylock(PCG_LOCK, &pc->flags); > > -} > > - > > static inline void unlock_page_cgroup(struct page_cgroup *pc) > > { > > bit_spin_unlock(PCG_LOCK, &pc->flags); > > Index: mmotm-2.6.30-Apr21/mm/memcontrol.c > > =================================================================== > > --- mmotm-2.6.30-Apr21.orig/mm/memcontrol.c > > +++ mmotm-2.6.30-Apr21/mm/memcontrol.c > > @@ -1148,8 +1148,7 @@ static int mem_cgroup_move_account(struc > > from_mz = mem_cgroup_zoneinfo(from, nid, zid); > > to_mz = mem_cgroup_zoneinfo(to, nid, zid); > > > > - if (!trylock_page_cgroup(pc)) > > - return ret; > > + lock_page_cgroup(pc); > > > > if (!PageCgroupUsed(pc)) > > goto out; > > But we can't remove that nasty `while (loop--)' thing? > every call which use isolate_lru_page() should handle isolatation failure. But its ok to remove force_empty_list()'s loop-- becasue we do retry in force_empty() force_empty() # does retry. -> force_empty_list() # does retry. > 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 ? But I'd like to do that in other patch than this patch bacause it chages force_empty()'s logic. 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/