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/fs/fs-writeback.c b/fs/fs-writeback.c
index 73acab4..bf10cbf 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -656,10 +656,14 @@
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 @@
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);