From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Sandeen Subject: Re: [PATCH] ext4: Don't allow lg prealloc list to be grow large. Date: Mon, 21 Jul 2008 14:37:19 -0500 Message-ID: <4884E56F.3010007@redhat.com> References: <1216633234-24194-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: cmm@us.ibm.com, tytso@mit.edu, linux-ext4@vger.kernel.org To: "Aneesh Kumar K.V" Return-path: Received: from mx1.redhat.com ([66.187.233.31]:50468 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755911AbYGUThr (ORCPT ); Mon, 21 Jul 2008 15:37:47 -0400 In-Reply-To: <1216633234-24194-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Aneesh Kumar K.V wrote: > The locality group prealloc list is freed only when there is a block allocation > failure. This can result in large number of per cpu locality group prealloc space > and also make the ext4_mb_use_preallocated expensive. Add a tunable max_lg_prealloc > which default to 1000. If we have more than 1000 Per-CPU prealloc space and if we > fail to find a suitable prealloc space during allocation we will now free all > the prealloc space in the locality group. It looks like this helps, but does not fare as well as the "perfectly tuned" default (where the prealloc size is a multiple of the 20k/5 block file size used in the test.) I've added a plot of a delalloc run with your patch to the graph at: http://people.redhat.com/esandeen/ext4/fs_mark.png -Eric