Commit 885bceca authored Feb 03, 2014 by Steven Whitehouse

GFS2: Plug on AIL flush



When we do a flush of the AIL list, we are writing out what is
likely to be a lot of small I/Os, which are possibly in an order
which is not ideal performance-wise. Since this is done by calling
filemap_fdatatwrite for each individual inode's address space there
is no overall plugging going on.

In addition to that, we do not always wait for AIL i/o when we flush
it, so that it is possible for things to get left behind on the queue.
By adding explicit plugging here, we reduce the chances of this
being an issues. A quick test using the AIL flush tracepoint shows a
small, but measurable improvement.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

parent 38dbfb59

fs/gfs2/log.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -18,6 +18,7 @@
		#include <linux/kthread.h>
		#include <linux/freezer.h>
		#include <linux/bio.h>
		#include <linux/blkdev.h>
		#include <linux/writeback.h>
		#include <linux/list_sort.h>

		@@ -145,8 +146,10 @@ void gfs2_ail1_flush(struct gfs2_sbd sdp, struct writeback_control wbc)
		{
		struct list_head *head = &sdp->sd_ail1_list;
		struct gfs2_trans *tr;
		struct blk_plug plug;

		trace_gfs2_ail_flush(sdp, wbc, 1);
		blk_start_plug(&plug);
		spin_lock(&sdp->sd_ail_lock);
		restart:
		list_for_each_entry_reverse(tr, head, tr_list) {
		@@ -156,6 +159,7 @@ restart:
		goto restart;
		}
		spin_unlock(&sdp->sd_ail_lock);
		blk_finish_plug(&plug);
		trace_gfs2_ail_flush(sdp, wbc, 0);
		}

Admin message