Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753329Ab0HBXvk (ORCPT ); Mon, 2 Aug 2010 19:51:40 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:48365 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751464Ab0HBXvc (ORCPT ); Mon, 2 Aug 2010 19:51:32 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Tue, 3 Aug 2010 08:46:38 +0900 From: KAMEZAWA Hiroyuki To: balbir@linux.vnet.ibm.com Cc: Greg Thelen , "linux-mm@kvack.org" , "nishimura@mxp.nes.nec.co.jp" , m-ikeda@ds.jp.nec.com, "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC][PATCH 7/7][memcg] use spin lock instead of bit_spin_lock in page_cgroup Message-Id: <20100803084638.f95f55ed.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20100802180911.GZ3863@balbir.in.ibm.com> References: <20100727165155.8b458b7f.kamezawa.hiroyu@jp.fujitsu.com> <20100727170225.64f78b15.kamezawa.hiroyu@jp.fujitsu.com> <20100802180911.GZ3863@balbir.in.ibm.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.3 (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: 2458 Lines: 68 On Mon, 2 Aug 2010 23:39:11 +0530 Balbir Singh wrote: > * Greg Thelen [2010-07-27 23:16:54]: > > > KAMEZAWA Hiroyuki writes: > > > > > From: KAMEZAWA Hiroyuki > > > > > > This patch replaces page_cgroup's bit_spinlock with spinlock. In general, > > > spinlock has good implementation than bit_spin_lock and we should use > > > it if we have a room for it. In 64bit arch, we have extra 4bytes. > > > Let's use it. > > > > > > Signed-off-by: KAMEZAWA Hiroyuki > > > -- > > > Index: mmotm-0719/include/linux/page_cgroup.h > > > =================================================================== > > > --- mmotm-0719.orig/include/linux/page_cgroup.h > > > +++ mmotm-0719/include/linux/page_cgroup.h > > > @@ -10,8 +10,14 @@ > > > * All page cgroups are allocated at boot or memory hotplug event, > > > * then the page cgroup for pfn always exists. > > > */ > > > +#ifdef CONFIG_64BIT > > > +#define PCG_HAS_SPINLOCK > > > +#endif > > > struct page_cgroup { > > > unsigned long flags; > > > +#ifdef PCG_HAS_SPINLOCK > > > + spinlock_t lock; > > > +#endif > > > unsigned short mem_cgroup; /* ID of assigned memory cgroup */ > > > unsigned short blk_cgroup; /* Not Used..but will be. */ > > > struct page *page; > > > @@ -90,6 +96,16 @@ static inline enum zone_type page_cgroup > > > return page_zonenum(pc->page); > > > } > > > > > > +#ifdef PCG_HAS_SPINLOCK > > > +static inline void lock_page_cgroup(struct page_cgroup *pc) > > > +{ > > > + spin_lock(&pc->lock); > > > +} > > > > This is minor issue, but this patch breaks usage of PageCgroupLocked(). > > Example from __mem_cgroup_move_account() cases panic: > > VM_BUG_ON(!PageCgroupLocked(pc)); > > > > I assume that this patch should also delete the following: > > - PCG_LOCK definition from page_cgroup.h > > - TESTPCGFLAG(Locked, LOCK) from page_cgroup.h > > - PCGF_LOCK from memcontrol.c > > > > > Good catch! But from my understanding of the code we use spinlock_t > only for 64 bit systems, so we still need the PCG* and TESTPGFLAGS. > The latest sets have proper calls. -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/