From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 11FF26B0095 for ; Tue, 21 Apr 2009 23:43:53 -0400 (EDT) Date: Tue, 21 Apr 2009 20:41:04 -0700 From: Andrew Morton Subject: Re: [PATCH] memcg: remove trylock_page_cgroup Message-Id: <20090421204104.faf9fc56.akpm@linux-foundation.org> In-Reply-To: <20090422121641.eb84a07e.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> 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 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? 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. -- 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