On Thu, Apr 21, 2011 at 03:17:57PM +0800, Christoph Hellwig wrote:
> Here's the inode_wb_list_lock splitup against current mainline:
So quick! I'll carry it and collect some numbers in my tests btw.
Thanks,
Fengguang
> ---
> From: Christoph Hellwig <hch@xxxxxx>
> Subject: [PATCH] writeback: split inode_wb_list_lock
>
> Split the global inode_wb_list_lock into a per-bdi_writeback list_lock,
> as it's currently the most contended lock in the system for metadata
> heavy workloads. I won't help for single-filesystem workloads for
> which we'll need the I/O-less balance_dirty_pages, but at least we
> can dedicate a cpu to spinning on each bdi now for larger systems.
>
> Based on earlier patches from Nick Piggin and Dave Chinner.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
>
> Index: linux-2.6/fs/fs-writeback.c
> ===================================================================
> --- linux-2.6.orig/fs/fs-writeback.c 2011-04-21 08:31:44.512334499 +0200
> +++ linux-2.6/fs/fs-writeback.c 2011-04-21 09:07:05.327511722 +0200
> @@ -180,12 +180,13 @@ void bdi_start_background_writeback(stru
> */
> void inode_wb_list_del(struct inode *inode)
> {
> - spin_lock(&inode_wb_list_lock);
> + struct backing_dev_info *bdi = inode_to_bdi(inode);
> +
> + spin_lock(&bdi->wb.list_lock);
> list_del_init(&inode->i_wb_list);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&bdi->wb.list_lock);
> }
>
> -
> /*
> * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
> * furthest end of its superblock's dirty-inode list.
> @@ -195,11 +196,9 @@ void inode_wb_list_del(struct inode *ino
> * the case then the inode must have been redirtied while it was being written
> * out and we don't reset its dirtied_when.
> */
> -static void redirty_tail(struct inode *inode)
> +static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
> {
> - struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
> -
> - assert_spin_locked(&inode_wb_list_lock);
> + assert_spin_locked(&wb->list_lock);
> if (!list_empty(&wb->b_dirty)) {
> struct inode *tail;
>
> @@ -213,11 +212,9 @@ static void redirty_tail(struct inode *i
> /*
> * requeue inode for re-scanning after bdi->b_io list is exhausted.
> */
> -static void requeue_io(struct inode *inode)
> +static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
> {
> - struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
> -
> - assert_spin_locked(&inode_wb_list_lock);
> + assert_spin_locked(&wb->list_lock);
> list_move(&inode->i_wb_list, &wb->b_more_io);
> }
>
> @@ -225,7 +222,7 @@ static void inode_sync_complete(struct i
> {
> /*
> * Prevent speculative execution through
> - * spin_unlock(&inode_wb_list_lock);
> + * spin_unlock(&wb->list_lock);
> */
>
> smp_mb();
> @@ -301,7 +298,7 @@ static void move_expired_inodes(struct l
> */
> static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
> {
> - assert_spin_locked(&inode_wb_list_lock);
> + assert_spin_locked(&wb->list_lock);
> list_splice_init(&wb->b_more_io, &wb->b_io);
> move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
> }
> @@ -316,7 +313,8 @@ static int write_inode(struct inode *ino
> /*
> * Wait for writeback on an inode to complete.
> */
> -static void inode_wait_for_writeback(struct inode *inode)
> +static void inode_wait_for_writeback(struct inode *inode,
> + struct bdi_writeback *wb)
> {
> DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
> wait_queue_head_t *wqh;
> @@ -324,15 +322,15 @@ static void inode_wait_for_writeback(str
> wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
> while (inode->i_state & I_SYNC) {
> spin_unlock(&inode->i_lock);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&wb->list_lock);
> __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&wb->list_lock);
> spin_lock(&inode->i_lock);
> }
> }
>
> /*
> - * Write out an inode's dirty pages. Called under inode_wb_list_lock and
> + * Write out an inode's dirty pages. Called under wb->list_lock and
> * inode->i_lock. Either the caller has an active reference on the inode or
> * the inode has I_WILL_FREE set.
> *
> @@ -343,13 +341,14 @@ static void inode_wait_for_writeback(str
> * livelocks, etc.
> */
> static int
> -writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
> +writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
> + struct writeback_control *wbc)
> {
> struct address_space *mapping = inode->i_mapping;
> unsigned dirty;
> int ret;
>
> - assert_spin_locked(&inode_wb_list_lock);
> + assert_spin_locked(&wb->list_lock);
> assert_spin_locked(&inode->i_lock);
>
> if (!atomic_read(&inode->i_count))
> @@ -367,14 +366,14 @@ writeback_single_inode(struct inode *ino
> * completed a full scan of b_io.
> */
> if (wbc->sync_mode != WB_SYNC_ALL) {
> - requeue_io(inode);
> + requeue_io(inode, wb);
> return 0;
> }
>
> /*
> * It's a data-integrity sync. We must wait.
> */
> - inode_wait_for_writeback(inode);
> + inode_wait_for_writeback(inode, wb);
> }
>
> BUG_ON(inode->i_state & I_SYNC);
> @@ -383,7 +382,7 @@ writeback_single_inode(struct inode *ino
> inode->i_state |= I_SYNC;
> inode->i_state &= ~I_DIRTY_PAGES;
> spin_unlock(&inode->i_lock);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&wb->list_lock);
>
> ret = do_writepages(mapping, wbc);
>
> @@ -414,7 +413,7 @@ writeback_single_inode(struct inode *ino
> ret = err;
> }
>
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&wb->list_lock);
> spin_lock(&inode->i_lock);
> inode->i_state &= ~I_SYNC;
> if (!(inode->i_state & I_FREEING)) {
> @@ -428,7 +427,7 @@ writeback_single_inode(struct inode *ino
> /*
> * slice used up: queue for next turn
> */
> - requeue_io(inode);
> + requeue_io(inode, wb);
> } else {
> /*
> * Writeback blocked by something other than
> @@ -437,7 +436,7 @@ writeback_single_inode(struct inode *ino
> * retrying writeback of the dirty page/inode
> * that cannot be performed immediately.
> */
> - redirty_tail(inode);
> + redirty_tail(inode, wb);
> }
> } else if (inode->i_state & I_DIRTY) {
> /*
> @@ -446,7 +445,7 @@ writeback_single_inode(struct inode *ino
> * submission or metadata updates after data IO
> * completion.
> */
> - redirty_tail(inode);
> + redirty_tail(inode, wb);
> } else {
> /*
> * The inode is clean. At this point we either have
> @@ -510,7 +509,7 @@ static int writeback_sb_inodes(struct su
> * superblock, move all inodes not belonging
> * to it back onto the dirty list.
> */
> - redirty_tail(inode);
> + redirty_tail(inode, wb);
> continue;
> }
>
> @@ -530,7 +529,7 @@ static int writeback_sb_inodes(struct su
> spin_lock(&inode->i_lock);
> if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
> spin_unlock(&inode->i_lock);
> - requeue_io(inode);
> + requeue_io(inode, wb);
> continue;
> }
>
> @@ -546,19 +545,19 @@ static int writeback_sb_inodes(struct su
> __iget(inode);
>
> pages_skipped = wbc->pages_skipped;
> - writeback_single_inode(inode, wbc);
> + writeback_single_inode(inode, wb, wbc);
> if (wbc->pages_skipped != pages_skipped) {
> /*
> * writeback is not making progress due to locked
> * buffers. Skip this inode for now.
> */
> - redirty_tail(inode);
> + redirty_tail(inode, wb);
> }
> spin_unlock(&inode->i_lock);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&wb->list_lock);
> iput(inode);
> cond_resched();
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&wb->list_lock);
> if (wbc->nr_to_write <= 0) {
> wbc->more_io = 1;
> return 1;
> @@ -577,7 +576,7 @@ void writeback_inodes_wb(struct bdi_writ
>
> if (!wbc->wb_start)
> wbc->wb_start = jiffies; /* livelock avoidance */
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&wb->list_lock);
> if (!wbc->for_kupdate || list_empty(&wb->b_io))
> queue_io(wb, wbc->older_than_this);
>
> @@ -586,7 +585,7 @@ void writeback_inodes_wb(struct bdi_writ
> struct super_block *sb = inode->i_sb;
>
> if (!pin_sb_for_writeback(sb)) {
> - requeue_io(inode);
> + requeue_io(inode, wb);
> continue;
> }
> ret = writeback_sb_inodes(sb, wb, wbc, false);
> @@ -595,7 +594,7 @@ void writeback_inodes_wb(struct bdi_writ
> if (ret)
> break;
> }
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&wb->list_lock);
> /* Leave any unwritten inodes on b_io */
> }
>
> @@ -604,11 +603,11 @@ static void __writeback_inodes_sb(struct
> {
> WARN_ON(!rwsem_is_locked(&sb->s_umount));
>
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&wb->list_lock);
> if (!wbc->for_kupdate || list_empty(&wb->b_io))
> queue_io(wb, wbc->older_than_this);
> writeback_sb_inodes(sb, wb, wbc, true);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&wb->list_lock);
> }
>
> /*
> @@ -747,15 +746,15 @@ static long wb_writeback(struct bdi_writ
> * become available for writeback. Otherwise
> * we'll just busyloop.
> */
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&wb->list_lock);
> if (!list_empty(&wb->b_more_io)) {
> inode = wb_inode(wb->b_more_io.prev);
> trace_wbc_writeback_wait(&wbc, wb->bdi);
> spin_lock(&inode->i_lock);
> - inode_wait_for_writeback(inode);
> + inode_wait_for_writeback(inode, wb);
> spin_unlock(&inode->i_lock);
> }
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&wb->list_lock);
> }
>
> return wrote;
> @@ -1092,10 +1091,10 @@ void __mark_inode_dirty(struct inode *in
> }
>
> spin_unlock(&inode->i_lock);
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&bdi->wb.list_lock);
> inode->dirtied_when = jiffies;
> list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&bdi->wb.list_lock);
>
> if (wakeup_bdi)
> bdi_wakeup_thread_delayed(bdi);
> @@ -1296,6 +1295,7 @@ EXPORT_SYMBOL(sync_inodes_sb);
> */
> int write_inode_now(struct inode *inode, int sync)
> {
> + struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
> int ret;
> struct writeback_control wbc = {
> .nr_to_write = LONG_MAX,
> @@ -1308,11 +1308,11 @@ int write_inode_now(struct inode *inode,
> wbc.nr_to_write = 0;
>
> might_sleep();
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&wb->list_lock);
> spin_lock(&inode->i_lock);
> - ret = writeback_single_inode(inode, &wbc);
> + ret = writeback_single_inode(inode, wb, &wbc);
> spin_unlock(&inode->i_lock);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&wb->list_lock);
> if (sync)
> inode_sync_wait(inode);
> return ret;
> @@ -1332,13 +1332,14 @@ EXPORT_SYMBOL(write_inode_now);
> */
> int sync_inode(struct inode *inode, struct writeback_control *wbc)
> {
> + struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
> int ret;
>
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&wb->list_lock);
> spin_lock(&inode->i_lock);
> - ret = writeback_single_inode(inode, wbc);
> + ret = writeback_single_inode(inode, wb, wbc);
> spin_unlock(&inode->i_lock);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&wb->list_lock);
> return ret;
> }
> EXPORT_SYMBOL(sync_inode);
> Index: linux-2.6/fs/inode.c
> ===================================================================
> --- linux-2.6.orig/fs/inode.c 2011-04-21 08:31:40.172358011 +0200
> +++ linux-2.6/fs/inode.c 2011-04-21 09:07:05.327511722 +0200
> @@ -37,7 +37,7 @@
> * inode_lru, inode->i_lru
> * inode_sb_list_lock protects:
> * sb->s_inodes, inode->i_sb_list
> - * inode_wb_list_lock protects:
> + * bdi->wb.list_lock protects:
> * bdi->wb.b_{dirty,io,more_io}, inode->i_wb_list
> * inode_hash_lock protects:
> * inode_hashtable, inode->i_hash
> @@ -48,7 +48,7 @@
> * inode->i_lock
> * inode_lru_lock
> *
> - * inode_wb_list_lock
> + * bdi->wb.list_lock
> * inode->i_lock
> *
> * inode_hash_lock
> @@ -111,7 +111,6 @@ static LIST_HEAD(inode_lru);
> static DEFINE_SPINLOCK(inode_lru_lock);
>
> __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_sb_list_lock);
> -__cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_wb_list_lock);
>
> /*
> * iprune_sem provides exclusion between the icache shrinking and the
> Index: linux-2.6/include/linux/writeback.h
> ===================================================================
> --- linux-2.6.orig/include/linux/writeback.h 2011-04-21 08:31:42.185680435 +0200
> +++ linux-2.6/include/linux/writeback.h 2011-04-21 09:07:05.327511722 +0200
> @@ -9,8 +9,6 @@
>
> struct backing_dev_info;
>
> -extern spinlock_t inode_wb_list_lock;
> -
> /*
> * fs/fs-writeback.c
> */
> Index: linux-2.6/mm/backing-dev.c
> ===================================================================
> --- linux-2.6.orig/mm/backing-dev.c 2011-04-21 08:31:44.532334389 +0200
> +++ linux-2.6/mm/backing-dev.c 2011-04-21 09:07:05.327511722 +0200
> @@ -45,6 +45,17 @@ static struct timer_list sync_supers_tim
> static int bdi_sync_supers(void *);
> static void sync_supers_timer_fn(unsigned long);
>
> +void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
> +{
> + if (wb1 < wb2) {
> + spin_lock(&wb1->list_lock);
> + spin_lock_nested(&wb2->list_lock, 1);
> + } else {
> + spin_lock(&wb2->list_lock);
> + spin_lock_nested(&wb1->list_lock, 1);
> + }
> +}
> +
> #ifdef CONFIG_DEBUG_FS
> #include <linux/debugfs.h>
> #include <linux/seq_file.h>
> @@ -67,14 +78,14 @@ static int bdi_debug_stats_show(struct s
> struct inode *inode;
>
> nr_wb = nr_dirty = nr_io = nr_more_io = 0;
> - spin_lock(&inode_wb_list_lock);
> + spin_lock(&wb->list_lock);
> list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
> nr_dirty++;
> list_for_each_entry(inode, &wb->b_io, i_wb_list)
> nr_io++;
> list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
> nr_more_io++;
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&wb->list_lock);
>
> global_dirty_limits(&background_thresh, &dirty_thresh);
> bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
> @@ -628,6 +639,7 @@ static void bdi_wb_init(struct bdi_write
> INIT_LIST_HEAD(&wb->b_dirty);
> INIT_LIST_HEAD(&wb->b_io);
> INIT_LIST_HEAD(&wb->b_more_io);
> + spin_lock_init(&wb->list_lock);
> setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
> }
>
> @@ -676,11 +688,12 @@ void bdi_destroy(struct backing_dev_info
> if (bdi_has_dirty_io(bdi)) {
> struct bdi_writeback *dst = &default_backing_dev_info.wb;
>
> - spin_lock(&inode_wb_list_lock);
> + bdi_lock_two(&bdi->wb, dst);
> list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
> list_splice(&bdi->wb.b_io, &dst->b_io);
> list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&bdi->wb.list_lock);
> + spin_unlock(&dst->list_lock);
> }
>
> bdi_unregister(bdi);
> Index: linux-2.6/mm/filemap.c
> ===================================================================
> --- linux-2.6.orig/mm/filemap.c 2011-04-21 08:31:42.159013915 +0200
> +++ linux-2.6/mm/filemap.c 2011-04-21 09:07:05.330845037 +0200
> @@ -80,7 +80,7 @@
> * ->i_mutex
> * ->i_alloc_sem (various)
> *
> - * inode_wb_list_lock
> + * bdi->wb.list_lock
> * sb_lock (fs/fs-writeback.c)
> * ->mapping->tree_lock (__sync_single_inode)
> *
> @@ -98,9 +98,9 @@
> * ->zone.lru_lock (check_pte_range->isolate_lru_page)
> * ->private_lock (page_remove_rmap->set_page_dirty)
> * ->tree_lock (page_remove_rmap->set_page_dirty)
> - * inode_wb_list_lock (page_remove_rmap->set_page_dirty)
> + * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
> * ->inode->i_lock (page_remove_rmap->set_page_dirty)
> - * inode_wb_list_lock (zap_pte_range->set_page_dirty)
> + * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
> * ->inode->i_lock (zap_pte_range->set_page_dirty)
> * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
> *
> Index: linux-2.6/mm/rmap.c
> ===================================================================
> --- linux-2.6.orig/mm/rmap.c 2011-04-21 08:31:41.519017382 +0200
> +++ linux-2.6/mm/rmap.c 2011-04-21 09:07:05.330845037 +0200
> @@ -32,11 +32,11 @@
> * mmlist_lock (in mmput, drain_mmlist and others)
> * mapping->private_lock (in __set_page_dirty_buffers)
> * inode->i_lock (in set_page_dirty's __mark_inode_dirty)
> - * inode_wb_list_lock (in set_page_dirty's __mark_inode_dirty)
> + * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
> * sb_lock (within inode_lock in fs/fs-writeback.c)
> * mapping->tree_lock (widely used, in set_page_dirty,
> * in arch-dependent flush_dcache_mmap_lock,
> - * within inode_wb_list_lock in __sync_single_inode)
> + * within bdi.wb->list_lock in __sync_single_inode)
> *
> * (code doesn't rely on that order so it could be switched around)
> * ->tasklist_lock
> Index: linux-2.6/fs/block_dev.c
> ===================================================================
> --- linux-2.6.orig/fs/block_dev.c 2011-04-21 08:31:44.522334444 +0200
> +++ linux-2.6/fs/block_dev.c 2011-04-21 09:07:05.330845037 +0200
> @@ -55,13 +55,16 @@ EXPORT_SYMBOL(I_BDEV);
> static void bdev_inode_switch_bdi(struct inode *inode,
> struct backing_dev_info *dst)
> {
> - spin_lock(&inode_wb_list_lock);
> + struct backing_dev_info *old = inode->i_data.backing_dev_info;
> +
> + bdi_lock_two(&old->wb, &dst->wb);
> spin_lock(&inode->i_lock);
> inode->i_data.backing_dev_info = dst;
> if (inode->i_state & I_DIRTY)
> list_move(&inode->i_wb_list, &dst->wb.b_dirty);
> spin_unlock(&inode->i_lock);
> - spin_unlock(&inode_wb_list_lock);
> + spin_unlock(&old->wb.list_lock);
> + spin_unlock(&dst->wb.list_lock);
> }
>
> static sector_t max_block(struct block_device *bdev)
> Index: linux-2.6/include/linux/backing-dev.h
> ===================================================================
> --- linux-2.6.orig/include/linux/backing-dev.h 2011-04-21 08:31:42.202347013 +0200
> +++ linux-2.6/include/linux/backing-dev.h 2011-04-21 09:07:05.330845037 +0200
> @@ -57,6 +57,7 @@ struct bdi_writeback {
> struct list_head b_dirty; /* dirty inodes */
> struct list_head b_io; /* parked for writeback */
> struct list_head b_more_io; /* parked for more writeback */
> + spinlock_t list_lock; /* protects the b_* lists. */
> };
>
> struct backing_dev_info {
> @@ -106,6 +107,7 @@ int bdi_writeback_thread(void *data);
> int bdi_has_dirty_io(struct backing_dev_info *bdi);
> void bdi_arm_supers_timer(void);
> void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi);
> +void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2);
>
> extern spinlock_t bdi_lock;
> extern struct list_head bdi_list;
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