Hi Fengguang:
On Fri, Oct 7, 2011 at 8:28 AM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
>
> On Wed, Sep 28, 2011 at 11:02:42PM +0800, Christoph Hellwig wrote:
> > Did we get to any conclusion on this series? I think having these
> > additional reasons in the tracepoints and the additional statistics
> > would be extremely useful for us who have to deal with writeback
> > issues frequently.
>
> I think we've reached reasonable agreements on the first patch, which
> has been split into two ones by Curt:
>
> 1/2 writeback: send work item to queue_io, move_expired_inodes
> 2/2 writeback: Add a 'reason' to wb_writeback_work
>
> I further incorporated some suggested changes by Jan and get the below
> updated patch 2/2, with changes
>
> - replace the tracing symbol array with wb_reason_name[]
> - remove the balance_dirty_pages reason (no longer exists)
> - rename @stat to @reason in the function declarations
> - rename "FS_free_space" to "fs_free_space"
>
> If no objections, I can push the two patches to linux-next tomorrow.
No objections on my part. Thanks for wrapping this up!
Curt
>
> Thanks,
> Fengguang
> ---
> Subject: writeback: Add a 'reason' to wb_writeback_work
> Date: Fri Oct 07 21:54:10 CST 2011
>
> From: Curt Wohlgemuth <curtw@xxxxxxxxxx>
>
> This creates a new 'reason' field in a wb_writeback_work
> structure, which unambiguously identifies who initiates
> writeback activity. A 'wb_reason' enumeration has been
> added to writeback.h, to enumerate the possible reasons.
>
> The 'writeback_work_class' and tracepoint event class and
> 'writeback_queue_io' tracepoints are updated to include the
> symbolic 'reason' in all trace events.
>
> And the 'writeback_inodes_sbXXX' family of routines has had
> a wb_stats parameter added to them, so callers can specify
> why writeback is being started.
>
> Acked-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Curt Wohlgemuth <curtw@xxxxxxxxxx>
> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> ---
>
> Changes since v2:
>
> - enum wb_stats renamed enum wb_reason
> - All WB_STAT_xxx enum constants now named WB_REASON_xxx
> - All 'reason' strings in tracepoints match the WB_REASON name
> - The change to send 'work' to queue_io, move_expired_inodes, and
> trace_writeback_queue_io are in a separate commit
>
> fs/btrfs/extent-tree.c | 3 +
> fs/buffer.c | 2 -
> fs/ext4/inode.c | 2 -
> fs/fs-writeback.c | 49 +++++++++++++++++++++--------
> fs/quota/quota.c | 2 -
> fs/sync.c | 4 +-
> fs/ubifs/budget.c | 2 -
> include/linux/backing-dev.h | 3 +
> include/linux/writeback.h | 32 +++++++++++++++---
> include/trace/events/writeback.h | 14 +++++---
> mm/backing-dev.c | 3 +
> mm/page-writeback.c | 3 +
> mm/vmscan.c | 3 +
> 13 files changed, 88 insertions(+), 34 deletions(-)
>
> --- linux-next.orig/fs/btrfs/extent-tree.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/fs/btrfs/extent-tree.c 2011-10-07 22:24:47.000000000 +0800
> @@ -3340,7 +3340,8 @@ static int shrink_delalloc(struct btrfs_
> smp_mb();
> nr_pages = min_t(unsigned long, nr_pages,
> root->fs_info->delalloc_bytes >> PAGE_CACHE_SHIFT);
> - writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages);
> + writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages,
> + WB_REASON_FS_FREE_SPACE);
>
> spin_lock(&space_info->lock);
> if (reserved > space_info->bytes_reserved)
> --- linux-next.orig/fs/buffer.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/fs/buffer.c 2011-10-07 22:24:47.000000000 +0800
> @@ -285,7 +285,7 @@ static void free_more_memory(void)
> struct zone *zone;
> int nid;
>
> - wakeup_flusher_threads(1024);
> + wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
> yield();
>
> for_each_online_node(nid) {
> --- linux-next.orig/fs/ext4/inode.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/fs/ext4/inode.c 2011-10-07 22:24:47.000000000 +0800
> @@ -2241,7 +2241,7 @@ static int ext4_nonda_switch(struct supe
> * start pushing delalloc when 1/2 of free blocks are dirty.
> */
> if (free_blocks < 2 * dirty_blocks)
> - writeback_inodes_sb_if_idle(sb);
> + writeback_inodes_sb_if_idle(sb, WB_REASON_FS_FREE_SPACE);
>
> return 0;
> }
> --- linux-next.orig/fs/fs-writeback.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/fs/fs-writeback.c 2011-10-07 22:24:47.000000000 +0800
> @@ -41,11 +41,23 @@ struct wb_writeback_work {
> unsigned int for_kupdate:1;
> unsigned int range_cyclic:1;
> unsigned int for_background:1;
> + enum wb_reason reason; /* why was writeback initiated? */
>
> struct list_head list; /* pending work list */
> struct completion *done; /* set if the caller waits */
> };
>
> +const char *wb_reason_name[] = {
> + [WB_REASON_BACKGROUND] = "background",
> + [WB_REASON_TRY_TO_FREE_PAGES] = "try_to_free_pages",
> + [WB_REASON_SYNC] = "sync",
> + [WB_REASON_PERIODIC] = "periodic",
> + [WB_REASON_LAPTOP_TIMER] = "laptop_timer",
> + [WB_REASON_FREE_MORE_MEM] = "free_more_memory",
> + [WB_REASON_FS_FREE_SPACE] = "fs_free_space",
> + [WB_REASON_FORKER_THREAD] = "forker_thread"
> +};
> +
> /*
> * Include the creation of the trace points after defining the
> * wb_writeback_work structure so that the definition remains local to this
> @@ -115,7 +127,7 @@ static void bdi_queue_work(struct backin
>
> static void
> __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
> - bool range_cyclic)
> + bool range_cyclic, enum wb_reason reason)
> {
> struct wb_writeback_work *work;
>
> @@ -135,6 +147,7 @@ __bdi_start_writeback(struct backing_dev
> work->sync_mode = WB_SYNC_NONE;
> work->nr_pages = nr_pages;
> work->range_cyclic = range_cyclic;
> + work->reason = reason;
>
> bdi_queue_work(bdi, work);
> }
> @@ -150,9 +163,10 @@ __bdi_start_writeback(struct backing_dev
> * completion. Caller need not hold sb s_umount semaphore.
> *
> */
> -void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
> +void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
> + enum wb_reason reason)
> {
> - __bdi_start_writeback(bdi, nr_pages, true);
> + __bdi_start_writeback(bdi, nr_pages, true, reason);
> }
>
> /**
> @@ -641,12 +655,14 @@ static long __writeback_inodes_wb(struct
> return wrote;
> }
>
> -long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages)
> +long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
> + enum wb_reason reason)
> {
> struct wb_writeback_work work = {
> .nr_pages = nr_pages,
> .sync_mode = WB_SYNC_NONE,
> .range_cyclic = 1,
> + .reason = reason,
> };
>
> spin_lock(&wb->list_lock);
> @@ -825,6 +841,7 @@ static long wb_check_background_flush(st
> .sync_mode = WB_SYNC_NONE,
> .for_background = 1,
> .range_cyclic = 1,
> + .reason = WB_REASON_BACKGROUND,
> };
>
> return wb_writeback(wb, &work);
> @@ -858,6 +875,7 @@ static long wb_check_old_data_flush(stru
> .sync_mode = WB_SYNC_NONE,
> .for_kupdate = 1,
> .range_cyclic = 1,
> + .reason = WB_REASON_PERIODIC,
> };
>
> return wb_writeback(wb, &work);
> @@ -976,7 +994,7 @@ int bdi_writeback_thread(void *data)
> * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
> * the whole world.
> */
> -void wakeup_flusher_threads(long nr_pages)
> +void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
> {
> struct backing_dev_info *bdi;
>
> @@ -989,7 +1007,7 @@ void wakeup_flusher_threads(long nr_page
> list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
> if (!bdi_has_dirty_io(bdi))
> continue;
> - __bdi_start_writeback(bdi, nr_pages, false);
> + __bdi_start_writeback(bdi, nr_pages, false, reason);
> }
> rcu_read_unlock();
> }
> @@ -1210,7 +1228,9 @@ static void wait_sb_inodes(struct super_
> * on how many (if any) will be written, and this function does not wait
> * for IO completion of submitted IO.
> */
> -void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr)
> +void writeback_inodes_sb_nr(struct super_block *sb,
> + unsigned long nr,
> + enum wb_reason reason)
> {
> DECLARE_COMPLETION_ONSTACK(done);
> struct wb_writeback_work work = {
> @@ -1219,6 +1239,7 @@ void writeback_inodes_sb_nr(struct super
> .tagged_writepages = 1,
> .done = &done,
> .nr_pages = nr,
> + .reason = reason,
> };
>
> WARN_ON(!rwsem_is_locked(&sb->s_umount));
> @@ -1235,9 +1256,9 @@ EXPORT_SYMBOL(writeback_inodes_sb_nr);
> * on how many (if any) will be written, and this function does not wait
> * for IO completion of submitted IO.
> */
> -void writeback_inodes_sb(struct super_block *sb)
> +void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
> {
> - return writeback_inodes_sb_nr(sb, get_nr_dirty_pages());
> + return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
> }
> EXPORT_SYMBOL(writeback_inodes_sb);
>
> @@ -1248,11 +1269,11 @@ EXPORT_SYMBOL(writeback_inodes_sb);
> * Invoke writeback_inodes_sb if no writeback is currently underway.
> * Returns 1 if writeback was started, 0 if not.
> */
> -int writeback_inodes_sb_if_idle(struct super_block *sb)
> +int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
> {
> if (!writeback_in_progress(sb->s_bdi)) {
> down_read(&sb->s_umount);
> - writeback_inodes_sb(sb);
> + writeback_inodes_sb(sb, reason);
> up_read(&sb->s_umount);
> return 1;
> } else
> @@ -1269,11 +1290,12 @@ EXPORT_SYMBOL(writeback_inodes_sb_if_idl
> * Returns 1 if writeback was started, 0 if not.
> */
> int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
> - unsigned long nr)
> + unsigned long nr,
> + enum wb_reason reason)
> {
> if (!writeback_in_progress(sb->s_bdi)) {
> down_read(&sb->s_umount);
> - writeback_inodes_sb_nr(sb, nr);
> + writeback_inodes_sb_nr(sb, nr, reason);
> up_read(&sb->s_umount);
> return 1;
> } else
> @@ -1297,6 +1319,7 @@ void sync_inodes_sb(struct super_block *
> .nr_pages = LONG_MAX,
> .range_cyclic = 0,
> .done = &done,
> + .reason = WB_REASON_SYNC,
> };
>
> WARN_ON(!rwsem_is_locked(&sb->s_umount));
> --- linux-next.orig/fs/quota/quota.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/fs/quota/quota.c 2011-10-07 22:24:47.000000000 +0800
> @@ -286,7 +286,7 @@ static int do_quotactl(struct super_bloc
> /* caller already holds s_umount */
> if (sb->s_flags & MS_RDONLY)
> return -EROFS;
> - writeback_inodes_sb(sb);
> + writeback_inodes_sb(sb, WB_REASON_SYNC);
> return 0;
> default:
> return -EINVAL;
> --- linux-next.orig/fs/sync.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/fs/sync.c 2011-10-07 22:24:47.000000000 +0800
> @@ -43,7 +43,7 @@ static int __sync_filesystem(struct supe
> if (wait)
> sync_inodes_sb(sb);
> else
> - writeback_inodes_sb(sb);
> + writeback_inodes_sb(sb, WB_REASON_SYNC);
>
> if (sb->s_op->sync_fs)
> sb->s_op->sync_fs(sb, wait);
> @@ -98,7 +98,7 @@ static void sync_filesystems(int wait)
> */
> SYSCALL_DEFINE0(sync)
> {
> - wakeup_flusher_threads(0);
> + wakeup_flusher_threads(0, WB_REASON_SYNC);
> sync_filesystems(0);
> sync_filesystems(1);
> if (unlikely(laptop_mode))
> --- linux-next.orig/fs/ubifs/budget.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/fs/ubifs/budget.c 2011-10-07 22:24:47.000000000 +0800
> @@ -63,7 +63,7 @@
> static void shrink_liability(struct ubifs_info *c, int nr_to_write)
> {
> down_read(&c->vfs_sb->s_umount);
> - writeback_inodes_sb(c->vfs_sb);
> + writeback_inodes_sb(c->vfs_sb, WB_REASON_FS_FREE_SPACE);
> up_read(&c->vfs_sb->s_umount);
> }
>
> --- linux-next.orig/include/linux/backing-dev.h 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/include/linux/backing-dev.h 2011-10-07 22:24:47.000000000 +0800
> @@ -118,7 +118,8 @@ int bdi_register(struct backing_dev_info
> int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
> void bdi_unregister(struct backing_dev_info *bdi);
> int bdi_setup_and_register(struct backing_dev_info *, char *, unsigned int);
> -void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages);
> +void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
> + enum wb_reason reason);
> void bdi_start_background_writeback(struct backing_dev_info *bdi);
> int bdi_writeback_thread(void *data);
> int bdi_has_dirty_io(struct backing_dev_info *bdi);
> --- linux-next.orig/include/linux/writeback.h 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/include/linux/writeback.h 2011-10-07 22:24:47.000000000 +0800
> @@ -39,6 +39,23 @@ enum writeback_sync_modes {
> };
>
> /*
> + * why some writeback work was initiated
> + */
> +enum wb_reason {
> + WB_REASON_BACKGROUND,
> + WB_REASON_TRY_TO_FREE_PAGES,
> + WB_REASON_SYNC,
> + WB_REASON_PERIODIC,
> + WB_REASON_LAPTOP_TIMER,
> + WB_REASON_FREE_MORE_MEM,
> + WB_REASON_FS_FREE_SPACE,
> + WB_REASON_FORKER_THREAD,
> +
> + WB_REASON_MAX,
> +};
> +extern const char *wb_reason_name[];
> +
> +/*
> * A control structure which tells the writeback code what to do. These are
> * always on the stack, and hence need no locking. They are always initialised
> * in a manner such that unspecified fields are set to zero.
> @@ -69,14 +86,17 @@ struct writeback_control {
> */
> struct bdi_writeback;
> int inode_wait(void *);
> -void writeback_inodes_sb(struct super_block *);
> -void writeback_inodes_sb_nr(struct super_block *, unsigned long nr);
> -int writeback_inodes_sb_if_idle(struct super_block *);
> -int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr);
> +void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
> +void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
> + enum wb_reason reason);
> +int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason);
> +int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr,
> + enum wb_reason reason);
> void sync_inodes_sb(struct super_block *);
> -long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages);
> +long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
> + enum wb_reason reason);
> long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
> -void wakeup_flusher_threads(long nr_pages);
> +void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
>
> /* writeback.h requires fs.h; it, too, is not included from here. */
> static inline void wait_on_inode(struct inode *inode)
> --- linux-next.orig/include/trace/events/writeback.h 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/include/trace/events/writeback.h 2011-10-07 22:24:47.000000000 +0800
> @@ -34,6 +34,7 @@ DECLARE_EVENT_CLASS(writeback_work_class
> __field(int, for_kupdate)
> __field(int, range_cyclic)
> __field(int, for_background)
> + __field(int, reason)
> ),
> TP_fast_assign(
> strncpy(__entry->name, dev_name(bdi->dev), 32);
> @@ -43,16 +44,18 @@ DECLARE_EVENT_CLASS(writeback_work_class
> __entry->for_kupdate = work->for_kupdate;
> __entry->range_cyclic = work->range_cyclic;
> __entry->for_background = work->for_background;
> + __entry->reason = work->reason;
> ),
> TP_printk("bdi %s: sb_dev %d:%d nr_pages=%ld sync_mode=%d "
> - "kupdate=%d range_cyclic=%d background=%d",
> + "kupdate=%d range_cyclic=%d background=%d reason=%s",
> __entry->name,
> MAJOR(__entry->sb_dev), MINOR(__entry->sb_dev),
> __entry->nr_pages,
> __entry->sync_mode,
> __entry->for_kupdate,
> __entry->range_cyclic,
> - __entry->for_background
> + __entry->for_background,
> + wb_reason_name[__entry->reason]
> )
> );
> #define DEFINE_WRITEBACK_WORK_EVENT(name) \
> @@ -165,6 +168,7 @@ TRACE_EVENT(writeback_queue_io,
> __field(unsigned long, older)
> __field(long, age)
> __field(int, moved)
> + __field(int, reason)
> ),
> TP_fast_assign(
> unsigned long *older_than_this = work->older_than_this;
> @@ -173,12 +177,14 @@ TRACE_EVENT(writeback_queue_io,
> __entry->age = older_than_this ?
> (jiffies - *older_than_this) * 1000 / HZ : -1;
> __entry->moved = moved;
> + __entry->reason = work->reason;
> ),
> - TP_printk("bdi %s: older=%lu age=%ld enqueue=%d",
> + TP_printk("bdi %s: older=%lu age=%ld enqueue=%d reason=%s",
> __entry->name,
> __entry->older, /* older_than_this in jiffies */
> __entry->age, /* older_than_this in relative milliseconds */
> - __entry->moved)
> + __entry->moved,
> + wb_reason_name[__entry->reason])
> );
>
> TRACE_EVENT(global_dirty_state,
> --- linux-next.orig/mm/backing-dev.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/mm/backing-dev.c 2011-10-07 22:24:47.000000000 +0800
> @@ -476,7 +476,8 @@ static int bdi_forker_thread(void *ptr)
> * the bdi from the thread. Hopefully 1024 is
> * large enough for efficient IO.
> */
> - writeback_inodes_wb(&bdi->wb, 1024);
> + writeback_inodes_wb(&bdi->wb, 1024,
> + WB_REASON_FORKER_THREAD);
> } else {
> /*
> * The spinlock makes sure we do not lose
> --- linux-next.orig/mm/page-writeback.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/mm/page-writeback.c 2011-10-07 22:24:47.000000000 +0800
> @@ -1304,7 +1304,8 @@ void laptop_mode_timer_fn(unsigned long
> * threshold
> */
> if (bdi_has_dirty_io(&q->backing_dev_info))
> - bdi_start_writeback(&q->backing_dev_info, nr_pages);
> + bdi_start_writeback(&q->backing_dev_info, nr_pages,
> + WB_REASON_LAPTOP_TIMER);
> }
>
> /*
> --- linux-next.orig/mm/vmscan.c 2011-10-07 22:23:35.000000000 +0800
> +++ linux-next/mm/vmscan.c 2011-10-07 22:24:47.000000000 +0800
> @@ -2181,7 +2181,8 @@ static unsigned long do_try_to_free_page
> */
> writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
> if (total_scanned > writeback_threshold) {
> - wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
> + wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
> + WB_REASON_TRY_TO_FREE_PAGES);
> sc->may_writepage = 1;
> }
>
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