答复: [PATCH] fs/writeback: do memory cgroup related writeback firstly

-----邮件原件-----
发件人: linux-fsdevel-owner@vger.kernel.org [mailto:linux-fsdevel-
owner@vger.kernel.org] 代表 Li RongQing
发送时间: 2018年7月4日 16:58
收件人: linux-fsdevel@vger.kernel.org; linux-mm@kvack.org
抄送: viro@zeniv.linux.org.uk
主题: [PATCH] fs/writeback: do memory cgroup related writeback firstly

When a mechine has hundreds of memory cgroups, and some cgroups
generate more or less dirty pages, but a cgroup of them has lots of memory
pressure and always tries to reclaim dirty page, then it will trigger all cgroups
to writeback, which is less efficient:

1.if the used memory in a memory cgroup reaches its limit, it is useless to
writeback other cgroups.
2.other cgroups can wait more time to merge write request

so replace the full flush with flushing writeback of memory cgroup whose
tasks tries to reclaim memory and trigger writeback, if nothing is writeback,
then start a full flush

Signed-off-by: Li RongQing <redacted>
---
 fs/fs-writeback.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index

abafc9bd4622..a27efc4711a9 100644

--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c

@@ -2001,6 +2001,28 @@ void wakeup_flusher_threads(enum wb_reason

reason)
 	if (blk_needs_flush_plug(current))
 		blk_schedule_flush_plug(current);

+#ifdef CONFIG_CGROUP_WRITEBACK
+	if (reason == WB_REASON_VMSCAN) {
+		int flush = 0;
+
+		rcu_read_lock();
+		list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
+			struct bdi_writeback *wb = wb_find_current(bdi);
+
+			if (wb && wb != &bdi->wb) {
+				if (wb_has_dirty_io(wb)) {
+					wb_start_writeback(wb, reason);
+					flush++;
+				}
+			}
+		}
+		rcu_read_unlock();
+
+		if (flush)
+			return;
+	}
+#endif
+
 	rcu_read_lock();
 	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
 		__wakeup_flusher_threads_bdi(bdi, reason);
--
2.16.2