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authorDave Chinner <dchinner@redhat.com>2010-07-07 13:24:07 +1000
committerJens Axboe <jaxboe@fusionio.com>2010-08-07 18:24:25 +0200
commit028c2dd184c097809986684f2f0627eea5529fea (patch)
treef6eb9e30a24d73597e5ce2a65b4638e9d1947504
parent455b2864686d3591b3b2f39eb46290c95f76471f (diff)
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writeback: Add tracing to balance_dirty_pages
Tracing high level background writeback events is good, but it doesn't give the entire picture. Add visibility into write throttling to catch IO dispatched by foreground throttling of processing dirtying lots of pages. Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
-rw-r--r--fs/fs-writeback.c5
-rw-r--r--include/trace/events/writeback.h64
-rw-r--r--mm/page-writeback.c4
3 files changed, 73 insertions, 0 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 73acab4dc2b..bf10cbf379d 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -656,10 +656,14 @@ static long wb_writeback(struct bdi_writeback *wb,
wbc.more_io = 0;
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
wbc.pages_skipped = 0;
+
+ trace_wbc_writeback_start(&wbc, wb->bdi);
if (work->sb)
__writeback_inodes_sb(work->sb, wb, &wbc);
else
writeback_inodes_wb(wb, &wbc);
+ trace_wbc_writeback_written(&wbc, wb->bdi);
+
work->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
@@ -687,6 +691,7 @@ static long wb_writeback(struct bdi_writeback *wb,
if (!list_empty(&wb->b_more_io)) {
inode = list_entry(wb->b_more_io.prev,
struct inode, i_list);
+ trace_wbc_writeback_wait(&wbc, wb->bdi);
inode_wait_for_writeback(inode);
}
spin_unlock(&inode_lock);
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 562fcae10d9..0be26acae06 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -85,6 +85,70 @@ DEFINE_WRITEBACK_EVENT(writeback_bdi_unregister);
DEFINE_WRITEBACK_EVENT(writeback_thread_start);
DEFINE_WRITEBACK_EVENT(writeback_thread_stop);
+DECLARE_EVENT_CLASS(wbc_class,
+ TP_PROTO(struct writeback_control *wbc, struct backing_dev_info *bdi),
+ TP_ARGS(wbc, bdi),
+ TP_STRUCT__entry(
+ __array(char, name, 32)
+ __field(long, nr_to_write)
+ __field(long, pages_skipped)
+ __field(int, sync_mode)
+ __field(int, nonblocking)
+ __field(int, encountered_congestion)
+ __field(int, for_kupdate)
+ __field(int, for_background)
+ __field(int, for_reclaim)
+ __field(int, range_cyclic)
+ __field(int, more_io)
+ __field(unsigned long, older_than_this)
+ __field(long, range_start)
+ __field(long, range_end)
+ ),
+
+ TP_fast_assign(
+ strncpy(__entry->name, dev_name(bdi->dev), 32);
+ __entry->nr_to_write = wbc->nr_to_write;
+ __entry->pages_skipped = wbc->pages_skipped;
+ __entry->sync_mode = wbc->sync_mode;
+ __entry->for_kupdate = wbc->for_kupdate;
+ __entry->for_background = wbc->for_background;
+ __entry->for_reclaim = wbc->for_reclaim;
+ __entry->range_cyclic = wbc->range_cyclic;
+ __entry->more_io = wbc->more_io;
+ __entry->older_than_this = wbc->older_than_this ?
+ *wbc->older_than_this : 0;
+ __entry->range_start = (long)wbc->range_start;
+ __entry->range_end = (long)wbc->range_end;
+ ),
+
+ TP_printk("bdi %s: towrt=%ld skip=%ld mode=%d kupd=%d "
+ "bgrd=%d reclm=%d cyclic=%d more=%d older=0x%lx "
+ "start=0x%lx end=0x%lx",
+ __entry->name,
+ __entry->nr_to_write,
+ __entry->pages_skipped,
+ __entry->sync_mode,
+ __entry->for_kupdate,
+ __entry->for_background,
+ __entry->for_reclaim,
+ __entry->range_cyclic,
+ __entry->more_io,
+ __entry->older_than_this,
+ __entry->range_start,
+ __entry->range_end)
+)
+
+#define DEFINE_WBC_EVENT(name) \
+DEFINE_EVENT(wbc_class, name, \
+ TP_PROTO(struct writeback_control *wbc, struct backing_dev_info *bdi), \
+ TP_ARGS(wbc, bdi))
+DEFINE_WBC_EVENT(wbc_writeback_start);
+DEFINE_WBC_EVENT(wbc_writeback_written);
+DEFINE_WBC_EVENT(wbc_writeback_wait);
+DEFINE_WBC_EVENT(wbc_balance_dirty_start);
+DEFINE_WBC_EVENT(wbc_balance_dirty_written);
+DEFINE_WBC_EVENT(wbc_balance_dirty_wait);
+
#endif /* _TRACE_WRITEBACK_H */
/* This part must be outside protection */
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 37498ef6154..d556cd829af 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -34,6 +34,7 @@
#include <linux/syscalls.h>
#include <linux/buffer_head.h>
#include <linux/pagevec.h>
+#include <trace/events/writeback.h>
/*
* After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
@@ -535,11 +536,13 @@ static void balance_dirty_pages(struct address_space *mapping,
* threshold otherwise wait until the disk writes catch
* up.
*/
+ trace_wbc_balance_dirty_start(&wbc, bdi);
if (bdi_nr_reclaimable > bdi_thresh) {
writeback_inodes_wb(&bdi->wb, &wbc);
pages_written += write_chunk - wbc.nr_to_write;
get_dirty_limits(&background_thresh, &dirty_thresh,
&bdi_thresh, bdi);
+ trace_wbc_balance_dirty_written(&wbc, bdi);
}
/*
@@ -565,6 +568,7 @@ static void balance_dirty_pages(struct address_space *mapping,
if (pages_written >= write_chunk)
break; /* We've done our duty */
+ trace_wbc_balance_dirty_wait(&wbc, bdi);
__set_current_state(TASK_INTERRUPTIBLE);
io_schedule_timeout(pause);