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Commit 730c213c authored by Eric Sandeen's avatar Eric Sandeen Committed by Theodore Ts'o
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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: default avatarEric Sandeen <sandeen@redhat.com>
Acked-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 8eea80d5

fs/ext4/mballoc.c

+5 −8
Original line number Diff line number Diff line
@@ -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;