Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030462AbWHXTL3 (ORCPT ); Thu, 24 Aug 2006 15:11:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030463AbWHXTL3 (ORCPT ); Thu, 24 Aug 2006 15:11:29 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:52142 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S1030462AbWHXTL2 (ORCPT ); Thu, 24 Aug 2006 15:11:28 -0400 Message-ID: <44EDF9DD.3040904@us.ibm.com> Date: Thu, 24 Aug 2006 12:11:25 -0700 From: Badari Pulavarty User-Agent: Thunderbird 1.5.0.5 (Windows/20060719) MIME-Version: 1.0 To: Christoph Hellwig , Badari Pulavarty , Herbert Xu , akpm@osdl.org, lkml , ext2-devel Subject: Re: [RFC][PATCH] Manage jbd allocations from its own slabs References: <1156374495.30517.5.camel@dyn9047017100.beaverton.ibm.com> <20060824185342.GA20935@infradead.org> In-Reply-To: <20060824185342.GA20935@infradead.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1375 Lines: 40 Christoph Hellwig wrote: > On Wed, Aug 23, 2006 at 04:08:15PM -0700, Badari Pulavarty wrote: > >> Hi, >> >> Here is the fix to "bh: Ensure bh fits within a page" problem >> caused by JBD. >> >> BTW, I realized that this problem can happen only with 1k, 2k >> filesystems - as 4k, 8k allocations disable slab debug >> automatically. But for completeness, I created slabs for those >> also. >> >> What do you think ? I ran basic tests and things are fine. >> > > Why can't you just use alloc_page? I bet the whole slab overhead > eats more memory than what's wasted when using alloc_pages. Especially > as the typical usecase is a 4k blocks filesystem with 4k pagesize > where the overhead of alloc_page is non-existant. > Yes. That was what proposed earlier. But for 1k, 2k allocations we end up wasting whole page. Isn't it ? Thats why I created right sized slabs and disable slab-debug. I guess, I can do this only for 1k, 2k filesystems and directly use alloc_page() for 4k and 8k - but that would make code ugly and also it doesn't handle cases for bigger base pagesize systems (64k power). Thanks, Badari - 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/