From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 3748E6B00A9 for ; Mon, 8 Mar 2010 23:51:09 -0500 (EST) Received: from d23relay04.au.ibm.com (d23relay04.au.ibm.com [202.81.31.246]) by e23smtp08.au.ibm.com (8.14.3/8.13.1) with ESMTP id o294p3WE003019 for ; Tue, 9 Mar 2010 15:51:03 +1100 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay04.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o294jLVC1032236 for ; Tue, 9 Mar 2010 15:45:22 +1100 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id o294p1uk013350 for ; Tue, 9 Mar 2010 15:51:02 +1100 Date: Tue, 9 Mar 2010 10:20:58 +0530 From: Balbir Singh Subject: Re: [PATCH mmotm 2.5/4] memcg: disable irq at page cgroup lock (Re: [PATCH -mmotm 3/4] memcg: dirty pages accounting and limiting infrastructure) Message-ID: <20100309045058.GX3073@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <1267995474-9117-4-git-send-email-arighi@develer.com> <20100308104447.c124c1ff.nishimura@mxp.nes.nec.co.jp> <20100308105641.e2e714f4.kamezawa.hiroyu@jp.fujitsu.com> <20100308111724.3e48aee3.nishimura@mxp.nes.nec.co.jp> <20100308113711.d7a249da.kamezawa.hiroyu@jp.fujitsu.com> <20100308170711.4d8b02f0.nishimura@mxp.nes.nec.co.jp> <20100308173100.b5997fd4.kamezawa.hiroyu@jp.fujitsu.com> <20100309001252.GB13490@linux> <20100309091914.4b5f6661.kamezawa.hiroyu@jp.fujitsu.com> <20100309102928.9f36d2bb.nishimura@mxp.nes.nec.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20100309102928.9f36d2bb.nishimura@mxp.nes.nec.co.jp> Sender: owner-linux-mm@kvack.org To: Daisuke Nishimura Cc: KAMEZAWA Hiroyuki , Andrea Righi , Vivek Goyal , Peter Zijlstra , Trond Myklebust , Suleiman Souhlal , Greg Thelen , "Kirill A. Shutemov" , Andrew Morton , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: * nishimura@mxp.nes.nec.co.jp [2010-03-09 10:29:28]: > On Tue, 9 Mar 2010 09:19:14 +0900, KAMEZAWA Hiroyuki wrote: > > On Tue, 9 Mar 2010 01:12:52 +0100 > > Andrea Righi wrote: > > > > > On Mon, Mar 08, 2010 at 05:31:00PM +0900, KAMEZAWA Hiroyuki wrote: > > > > On Mon, 8 Mar 2010 17:07:11 +0900 > > > > Daisuke Nishimura wrote: > > > > > > > > > On Mon, 8 Mar 2010 11:37:11 +0900, KAMEZAWA Hiroyuki wrote: > > > > > > On Mon, 8 Mar 2010 11:17:24 +0900 > > > > > > Daisuke Nishimura wrote: > > > > > > > > > > > > > > But IIRC, clear_writeback is done under treelock.... No ? > > > > > > > > > > > > > > > The place where NR_WRITEBACK is updated is out of tree_lock. > > > > > > > > > > > > > > 1311 int test_clear_page_writeback(struct page *page) > > > > > > > 1312 { > > > > > > > 1313 struct address_space *mapping = page_mapping(page); > > > > > > > 1314 int ret; > > > > > > > 1315 > > > > > > > 1316 if (mapping) { > > > > > > > 1317 struct backing_dev_info *bdi = mapping->backing_dev_info; > > > > > > > 1318 unsigned long flags; > > > > > > > 1319 > > > > > > > 1320 spin_lock_irqsave(&mapping->tree_lock, flags); > > > > > > > 1321 ret = TestClearPageWriteback(page); > > > > > > > 1322 if (ret) { > > > > > > > 1323 radix_tree_tag_clear(&mapping->page_tree, > > > > > > > 1324 page_index(page), > > > > > > > 1325 PAGECACHE_TAG_WRITEBACK); > > > > > > > 1326 if (bdi_cap_account_writeback(bdi)) { > > > > > > > 1327 __dec_bdi_stat(bdi, BDI_WRITEBACK); > > > > > > > 1328 __bdi_writeout_inc(bdi); > > > > > > > 1329 } > > > > > > > 1330 } > > > > > > > 1331 spin_unlock_irqrestore(&mapping->tree_lock, flags); > > > > > > > 1332 } else { > > > > > > > 1333 ret = TestClearPageWriteback(page); > > > > > > > 1334 } > > > > > > > 1335 if (ret) > > > > > > > 1336 dec_zone_page_state(page, NR_WRITEBACK); > > > > > > > 1337 return ret; > > > > > > > 1338 } > > > > > > > > > > > > We can move this up to under tree_lock. Considering memcg, all our target has "mapping". > > > > > > > > > > > > If we newly account bounce-buffers (for NILFS, FUSE, etc..), which has no ->mapping, > > > > > > we need much more complex new charge/uncharge theory. > > > > > > > > > > > > But yes, adding new lock scheme seems complicated. (Sorry Andrea.) > > > > > > My concerns is performance. We may need somehing new re-implementation of > > > > > > locks/migrate/charge/uncharge. > > > > > > > > > > > I agree. Performance is my concern too. > > > > > > > > > > I made a patch below and measured the time(average of 10 times) of kernel build > > > > > on tmpfs(make -j8 on 8 CPU machine with 2.6.33 defconfig). > > > > > > > > > > > > > > > - root cgroup: 190.47 sec > > > > > - child cgroup: 192.81 sec > > > > > > > > > > > > > > > - root cgroup: 191.06 sec > > > > > - child cgroup: 193.06 sec > > > > > > > > > > Hmm... about 0.3% slower for root, 0.1% slower for child. > > > > > > > > > > > > > Hmm...accepatable ? (sounds it's in error-range) > > > > > > > > BTW, why local_irq_disable() ? > > > > local_irq_save()/restore() isn't better ? > > > > > > Probably there's not the overhead of saving flags? > > maybe. > > > > > Anyway, it would make the code much more readable... > > > > > ok. > > > > please go ahead in this direction. Nishimura-san, would you post an > > independent patch ? If no, Andrea-san, please. > > > This is the updated version. > > Andrea-san, can you merge this into your patch set ? > Please please measure the performance overhead of this change. -- Three Cheers, Balbir -- 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