ext4: use percpu data structures for lg_prealloc_list

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 <sandeen@redhat.com>
Acked-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 9122271..14ebd57 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2541,17 +2541,16 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
        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]);
@@ -2648,8 +2647,7 @@ int ext4_mb_release(struct super_block *sb)
                                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);
 
@@ -4106,8 +4104,7 @@ static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
         * 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;