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>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 37498ef..d556cd8 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 @@
* 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 @@
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);