From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932397AbWDZUJi (ORCPT ); Wed, 26 Apr 2006 16:09:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932398AbWDZUJi (ORCPT ); Wed, 26 Apr 2006 16:09:38 -0400 Received: from smtp.osdl.org ([65.172.181.4]:6623 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S932397AbWDZUJh (ORCPT ); Wed, 26 Apr 2006 16:09:37 -0400 Date: Wed, 26 Apr 2006 13:12:00 -0700 From: Andrew Morton To: Jens Axboe Cc: torvalds@osdl.org, linux-kernel@vger.kernel.org, npiggin@suse.de, linux-mm@kvack.org Subject: Re: Lockless page cache test results Message-Id: <20060426131200.516cbabc.akpm@osdl.org> In-Reply-To: <20060426191557.GA9211@suse.de> References: <20060426135310.GB5083@suse.de> <20060426095511.0cc7a3f9.akpm@osdl.org> <20060426174235.GC5002@suse.de> <20060426111054.2b4f1736.akpm@osdl.org> <20060426191557.GA9211@suse.de> X-Mailer: Sylpheed version 1.0.0 (GTK+ 1.2.10; i386-vine-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe wrote: > > With a 16-page gang lookup in splice, the top profile for the 4-client > case (which is now at 4GiB/sec instead of 3) are: > > samples % symbol name > 30396 36.7217 __do_page_cache_readahead > 25843 31.2212 find_get_pages_contig > 9699 11.7174 default_idle __do_page_cache_readahead() should use gang lookup. We never got around to that, mainly because nothing really demonstrated a need. It's a problem that __do_page_cache_readahead() is being called at all - with everything in pagecache we should be auto-turning-off readahead. This happens because splice is calling the low-level do_pagecache_readahead(). If you convert it to use page_cache_readahead(), that will all vanish if readahead is working right.