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quota: Reduce contention on dq_data_lock

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dq_data_lock is currently used to protect all modifications of quota
accounting information, consistency of quota accounting on the inode,
and dquot pointers from inode. As a result contention on the lock can be
pretty heavy.

Reduce the contention on the lock by protecting quota accounting
information by a new dquot->dq_dqb_lock and consistency of quota
accounting with inode usage by inode->i_lock.

This change reduces time to create 500000 files on ext4 on ramdisk by 50
different processes in separate directories by 6% when user quota is
turned on. When those 50 processes belong to 50 different users, the
improvement is about 9%.

Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jan Kara
2017-08-07 13:19:50 +02:00
parent f4a8116a4c
commit 7b9ca4c61b
6 changed files with 186 additions and 132 deletions
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4
fs/ext4/super.c
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@@ -5194,7 +5194,7 @@ static int ext4_statfs_project(struct super_block *sb,
dquot = dqget(sb, qid);
if (IS_ERR(dquot))
return PTR_ERR(dquot);
spin_lock(&dq_data_lock);
spin_lock(&dquot->dq_dqb_lock);
limit = (dquot->dq_dqb.dqb_bsoftlimit ?
dquot->dq_dqb.dqb_bsoftlimit :
@@ -5217,7 +5217,7 @@ static int ext4_statfs_project(struct super_block *sb,
(buf->f_files - dquot->dq_dqb.dqb_curinodes) : 0;
}
spin_unlock(&dq_data_lock);
spin_unlock(&dquot->dq_dqb_lock);
dqput(dquot);
return 0;
}