From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from edge05.upc.biz ([192.168.13.212]) by viefep19-int.chello.at (InterMail vM.7.08.02.02 201-2186-121-104-20070414) with ESMTP id <20080812072229.SDPQ16862.viefep19-int.chello.at@edge05.upc.biz> for ; Tue, 12 Aug 2008 09:22:29 +0200 Subject: Re: [PATCH 05/30] mm: slb: add knowledge of reserve pages From: Peter Zijlstra In-Reply-To: <18593.8466.965002.476705@notabene.brown> References: <20080724140042.408642539@chello.nl> <20080724141529.635920366@chello.nl> <18593.8466.965002.476705@notabene.brown> Content-Type: text/plain Date: Tue, 12 Aug 2008 09:22:30 +0200 Message-Id: <1218525750.10800.156.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Neil Brown Cc: Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, trond.myklebust@fys.uio.no, Daniel Lezcano , Pekka Enberg List-ID: On Tue, 2008-08-12 at 15:35 +1000, Neil Brown wrote: > On Thursday July 24, a.p.zijlstra@chello.nl wrote: > > Restrict objects from reserve slabs (ALLOC_NO_WATERMARKS) to allocation > > contexts that are entitled to it. This is done to ensure reserve pages don't > > leak out and get consumed. > > This looks good (we are still missing slob though, aren't we :-( ) I actually have that now, just needs some testing.. > > @@ -1526,7 +1540,7 @@ load_freelist: > > object = c->page->freelist; > > if (unlikely(!object)) > > goto another_slab; > > - if (unlikely(SLABDEBUG && PageSlubDebug(c->page))) > > + if (unlikely(PageSlubDebug(c->page) || c->reserve)) > > goto debug; > > This looks suspiciously like debugging code that you have left in. > Is it?? Its not, we need to force slub into the debug slow path when we have a reserve page, otherwise we cannot do the permission check on each allocation. > > @@ -265,7 +267,8 @@ struct array_cache { > > unsigned int avail; > > unsigned int limit; > > unsigned int batchcount; > > - unsigned int touched; > > + unsigned int touched:1, > > + reserve:1; > > This sort of thing always worries me. > It is a per-cpu data structure so you won't get SMP races corrupting > fields. But you do get read-modify-write in place of simple updates. > I guess it's not a problem.. But it worries me :-) Right,.. do people prefer I just add another int? -- 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