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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>
This commit is contained in:
Dave Chinner 2010-07-07 13:24:07 +10:00 committed by Jens Axboe
parent 455b286468
commit 028c2dd184
3 changed files with 73 additions and 0 deletions
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5
fs/fs-writeback.c
View File

@ -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);

64
include/trace/events/writeback.h
View File

@ -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 */

4
mm/page-writeback.c
View File

@ -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);