![Dave Chinner](/assets/img/avatar_default.png)
group and project quota hints are currently stored on the user dquot. If we are attaching quotas to the inode, then the group and project dquots are stored as hints on the user dquot to save having to look them up again later. The thing is, the hints are not used for that inode for the rest of the life of the inode - the dquots are attached directly to the inode itself - so the only time the hints are used is when an inode first has dquots attached. When the hints on the user dquot don't match the dquots being attache dto the inode, they are then removed and replaced with the new hints. If a user is concurrently modifying files in different group and/or project contexts, then this leads to thrashing of the hints attached to user dquot. If user quotas are not enabled, then hints are never even used. So, if the hints are used to avoid the cost of the lookup, is the cost of the lookup significant enough to justify the hint infrstructure? Maybe it was once, when there was a global quota manager shared between all XFS filesystems and was hash table based. However, lookups are now much simpler, requiring only a single lock and radix tree lookup local to the filesystem and no hash or LRU manipulations to be made. Hence the cost of lookup is much lower than when hints were implemented. Turns out that benchmarks show that, too, with thir being no differnce in performance when doing file creation workloads as a single user with user, group and project quotas enabled - the hints do not make the code go any faster. In fact, removing the hints shows a 2-3% reduction in the time it takes to create 50 million inodes.... So, let's just get rid of the hints and the complexity around them. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Dave Chinner <david@fromorbit.com>
174 lines
5.2 KiB
C
174 lines
5.2 KiB
C
/*
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* Copyright (c) 2000-2005 Silicon Graphics, Inc.
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* All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef __XFS_DQUOT_H__
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#define __XFS_DQUOT_H__
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/*
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* Dquots are structures that hold quota information about a user or a group,
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* much like inodes are for files. In fact, dquots share many characteristics
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* with inodes. However, dquots can also be a centralized resource, relative
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* to a collection of inodes. In this respect, dquots share some characteristics
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* of the superblock.
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* XFS dquots exploit both those in its algorithms. They make every attempt
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* to not be a bottleneck when quotas are on and have minimal impact, if any,
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* when quotas are off.
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*/
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struct xfs_mount;
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struct xfs_trans;
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enum {
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XFS_QLOWSP_1_PCNT = 0,
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XFS_QLOWSP_3_PCNT,
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XFS_QLOWSP_5_PCNT,
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XFS_QLOWSP_MAX
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};
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/*
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* The incore dquot structure
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*/
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typedef struct xfs_dquot {
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uint dq_flags; /* various flags (XFS_DQ_*) */
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struct list_head q_lru; /* global free list of dquots */
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struct xfs_mount*q_mount; /* filesystem this relates to */
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struct xfs_trans*q_transp; /* trans this belongs to currently */
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uint q_nrefs; /* # active refs from inodes */
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xfs_daddr_t q_blkno; /* blkno of dquot buffer */
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int q_bufoffset; /* off of dq in buffer (# dquots) */
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xfs_fileoff_t q_fileoffset; /* offset in quotas file */
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xfs_disk_dquot_t q_core; /* actual usage & quotas */
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xfs_dq_logitem_t q_logitem; /* dquot log item */
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xfs_qcnt_t q_res_bcount; /* total regular nblks used+reserved */
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xfs_qcnt_t q_res_icount; /* total inos allocd+reserved */
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xfs_qcnt_t q_res_rtbcount;/* total realtime blks used+reserved */
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xfs_qcnt_t q_prealloc_lo_wmark;/* prealloc throttle wmark */
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xfs_qcnt_t q_prealloc_hi_wmark;/* prealloc disabled wmark */
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int64_t q_low_space[XFS_QLOWSP_MAX];
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struct mutex q_qlock; /* quota lock */
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struct completion q_flush; /* flush completion queue */
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atomic_t q_pincount; /* dquot pin count */
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wait_queue_head_t q_pinwait; /* dquot pinning wait queue */
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} xfs_dquot_t;
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/*
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* Lock hierarchy for q_qlock:
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* XFS_QLOCK_NORMAL is the implicit default,
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* XFS_QLOCK_NESTED is the dquot with the higher id in xfs_dqlock2
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*/
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enum {
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XFS_QLOCK_NORMAL = 0,
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XFS_QLOCK_NESTED,
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};
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/*
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* Manage the q_flush completion queue embedded in the dquot. This completion
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* queue synchronizes processes attempting to flush the in-core dquot back to
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* disk.
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*/
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static inline void xfs_dqflock(xfs_dquot_t *dqp)
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{
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wait_for_completion(&dqp->q_flush);
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}
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static inline int xfs_dqflock_nowait(xfs_dquot_t *dqp)
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{
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return try_wait_for_completion(&dqp->q_flush);
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}
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static inline void xfs_dqfunlock(xfs_dquot_t *dqp)
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{
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complete(&dqp->q_flush);
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}
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static inline int xfs_dqlock_nowait(struct xfs_dquot *dqp)
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{
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return mutex_trylock(&dqp->q_qlock);
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}
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static inline void xfs_dqlock(struct xfs_dquot *dqp)
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{
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mutex_lock(&dqp->q_qlock);
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}
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static inline void xfs_dqunlock(struct xfs_dquot *dqp)
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{
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mutex_unlock(&dqp->q_qlock);
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}
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static inline int xfs_this_quota_on(struct xfs_mount *mp, int type)
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{
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switch (type & XFS_DQ_ALLTYPES) {
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case XFS_DQ_USER:
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return XFS_IS_UQUOTA_ON(mp);
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case XFS_DQ_GROUP:
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return XFS_IS_GQUOTA_ON(mp);
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case XFS_DQ_PROJ:
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return XFS_IS_PQUOTA_ON(mp);
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default:
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return 0;
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}
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}
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static inline xfs_dquot_t *xfs_inode_dquot(struct xfs_inode *ip, int type)
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{
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switch (type & XFS_DQ_ALLTYPES) {
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case XFS_DQ_USER:
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return ip->i_udquot;
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case XFS_DQ_GROUP:
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return ip->i_gdquot;
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case XFS_DQ_PROJ:
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return ip->i_pdquot;
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default:
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return NULL;
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}
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}
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#define XFS_DQ_IS_LOCKED(dqp) (mutex_is_locked(&((dqp)->q_qlock)))
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#define XFS_DQ_IS_DIRTY(dqp) ((dqp)->dq_flags & XFS_DQ_DIRTY)
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#define XFS_QM_ISUDQ(dqp) ((dqp)->dq_flags & XFS_DQ_USER)
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#define XFS_QM_ISPDQ(dqp) ((dqp)->dq_flags & XFS_DQ_PROJ)
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#define XFS_QM_ISGDQ(dqp) ((dqp)->dq_flags & XFS_DQ_GROUP)
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extern int xfs_qm_dqread(struct xfs_mount *, xfs_dqid_t, uint,
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uint, struct xfs_dquot **);
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extern void xfs_qm_dqdestroy(xfs_dquot_t *);
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extern int xfs_qm_dqflush(struct xfs_dquot *, struct xfs_buf **);
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extern void xfs_qm_dqunpin_wait(xfs_dquot_t *);
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extern void xfs_qm_adjust_dqtimers(xfs_mount_t *,
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xfs_disk_dquot_t *);
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extern void xfs_qm_adjust_dqlimits(struct xfs_mount *,
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struct xfs_dquot *);
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extern int xfs_qm_dqget(xfs_mount_t *, xfs_inode_t *,
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xfs_dqid_t, uint, uint, xfs_dquot_t **);
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extern void xfs_qm_dqput(xfs_dquot_t *);
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extern void xfs_dqlock2(struct xfs_dquot *, struct xfs_dquot *);
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extern void xfs_dquot_set_prealloc_limits(struct xfs_dquot *);
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static inline struct xfs_dquot *xfs_qm_dqhold(struct xfs_dquot *dqp)
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{
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xfs_dqlock(dqp);
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dqp->q_nrefs++;
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xfs_dqunlock(dqp);
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return dqp;
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}
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#endif /* __XFS_DQUOT_H__ */
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