On Wed 16-08-17 14:17:23, Andreas Dilger wrote:
> On Aug 16, 2017, at 9:41 AM, Jan Kara <jack@xxxxxxx> wrote:
> >
> > 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@xxxxxxx>
> >
> > @@ -1604,33 +1628,41 @@ int __dquot_alloc_space(struct inode *inode, qsize_t number, int flags)
> >
> > dquots = i_dquot(inode);
> > index = srcu_read_lock(&dquot_srcu);
> > - spin_lock(&dq_data_lock);
> > + spin_lock(&inode->i_lock);
> > for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
> > if (!dquots[cnt])
> > continue;
> > - ret = check_bdq(dquots[cnt], number,
> > - !(flags & DQUOT_SPACE_WARN), &warn[cnt]);
> > - if (ret && !(flags & DQUOT_SPACE_NOFAIL)) {
> > - spin_unlock(&dq_data_lock);
> > + if (flags & DQUOT_SPACE_RESERVE) {
> > + ret = dquot_add_space(dquots[cnt], 0, number, flags,
> > + &warn[cnt]);
> > + } else {
> > + ret = dquot_add_space(dquots[cnt], number, 0, flags,
> > + &warn[cnt]);
> > + }
>
> Minor nit - no need for braces around these single-line functions.
Yeah, but I prefer braces in case lines are wrapped...
> > diff --git a/include/linux/quota.h b/include/linux/quota.h
> > index eccc1cb6274e..4b5180efff21 100644
> > --- a/include/linux/quota.h
> > +++ b/include/linux/quota.h
> > @@ -298,6 +298,7 @@ struct dquot {
> > struct list_head dq_free; /* Free list element */
> > struct list_head dq_dirty; /* List of dirty dquots */
> > struct mutex dq_lock; /* dquot IO lock */
> > + spinlock_t dq_dqb_lock; /* Lock protecting dq_dqb changes */
>
> Might be good to have a comment at mem_dqblk that dq_lock is used for locking?
OK, will do.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
