From: Eric Sandeen Subject: [PATCH] use percpu data for lg_prealloc_list Date: Wed, 13 Aug 2008 14:11:54 -0500 Message-ID: <48A331FA.6070602@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Aneesh Kumar K.V" To: ext4 development Return-path: Received: from mx1.redhat.com ([66.187.233.31]:44765 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751436AbYHMTOL (ORCPT ); Wed, 13 Aug 2008 15:14:11 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: lg_prealloc_list seems to cry out for a per-cpu data structure; on a large smp system I think this should be better. I've lightly tested this change on a 4-cpu system. Comments welcome... Signed-off-by: Eric Sandeen --- ndex: linux-2.6/fs/ext4/mballoc.c =================================================================== --- linux-2.6.orig/fs/ext4/mballoc.c 2008-08-04 15:30:30.000000000 -0500 +++ linux-2.6/fs/ext4/mballoc.c 2008-08-13 13:48:33.224165751 -0500 @@ -2540,17 +2540,16 @@ int ext4_mb_init(struct super_block *sb, sbi->s_mb_history_filter = EXT4_MB_HISTORY_DEFAULT; sbi->s_mb_group_prealloc = MB_DEFAULT_GROUP_PREALLOC; - i = sizeof(struct ext4_locality_group) * nr_cpu_ids; - sbi->s_locality_groups = kmalloc(i, GFP_KERNEL); + sbi->s_locality_groups = alloc_percpu(struct ext4_locality_group); if (sbi->s_locality_groups == NULL) { clear_opt(sbi->s_mount_opt, MBALLOC); kfree(sbi->s_mb_offsets); kfree(sbi->s_mb_maxs); return -ENOMEM; } - for (i = 0; i < nr_cpu_ids; i++) { + for_each_possible_cpu(i) { struct ext4_locality_group *lg; - lg = &sbi->s_locality_groups[i]; + lg = per_cpu_ptr(sbi->s_locality_groups, i); mutex_init(&lg->lg_mutex); for (j = 0; j < PREALLOC_TB_SIZE; j++) INIT_LIST_HEAD(&lg->lg_prealloc_list[j]); @@ -2647,8 +2646,7 @@ int ext4_mb_release(struct super_block * atomic_read(&sbi->s_mb_discarded)); } - kfree(sbi->s_locality_groups);