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.
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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