ext4: use percpu data structures for lg_prealloc_list From: Eric Sandeen 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. Signed-off-by: Eric Sandeen Acked-by: Aneesh Kumar K.V Signed-off-by: "Theodore Ts'o" --- mballoc.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) Index: 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); - + free_percpu(sbi->s_locality_groups); ext4_mb_history_release(sb); ext4_mb_destroy_per_dev_proc(sb); @@ -4055,8 +4053,7 @@ static void ext4_mb_group_or_file(struct * per cpu locality group is to reduce the contention between block * request from multiple CPUs. */ - ac->ac_lg = &sbi->s_locality_groups[get_cpu()]; - put_cpu(); + ac->ac_lg = per_cpu_ptr(sbi->s_locality_groups, raw_smp_processor_id()); /* we're going to use group allocation */ ac->ac_flags |= EXT4_MB_HINT_GROUP_ALLOC;