From: Johannes Weiner <hannes@cmpxchg.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>, Michal Hocko <mhocko@suse.com>,
Minchan Kim <minchan.kim@gmail.com>,
Rik van Riel <riel@redhat.com>,
Hillf Danton <hillf.zj@alibaba-inc.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH 7/7] mm: vmscan: move dirty pages out of the way until they're flushed fix
Date: Thu, 2 Feb 2017 14:19:57 -0500 [thread overview]
Message-ID: <20170202191957.22872-8-hannes@cmpxchg.org> (raw)
In-Reply-To: <20170202191957.22872-1-hannes@cmpxchg.org>
Mention the trade-off between waiting for writeback and potentially
causing hot cache refaults in the code where we make this decisions
and activate writeback pages.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
mm/vmscan.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 70103f411247..ae3d982216b5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1056,6 +1056,15 @@ static unsigned long shrink_page_list(struct list_head *page_list,
* throttling so we could easily OOM just because too many
* pages are in writeback and there is nothing else to
* reclaim. Wait for the writeback to complete.
+ *
+ * In cases 1) and 2) we activate the pages to get them out of
+ * the way while we continue scanning for clean pages on the
+ * inactive list and refilling from the active list. The
+ * observation here is that waiting for disk writes is more
+ * expensive than potentially causing reloads down the line.
+ * Since they're marked for immediate reclaim, they won't put
+ * memory pressure on the cache working set any longer than it
+ * takes to write them to disk.
*/
if (PageWriteback(page)) {
/* Case 1 above */
--
2.11.0
next prev parent reply other threads:[~2017-02-02 19:20 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-02 19:19 [PATCH 0/7] mm: vmscan: fix kswapd writeback regression v2 Johannes Weiner
2017-02-02 19:19 ` [PATCH 1/7] mm: vmscan: scan dirty pages even in laptop mode Johannes Weiner
2017-02-02 19:19 ` [PATCH 2/7] mm: vmscan: kick flushers when we encounter dirty pages on the LRU Johannes Weiner
2017-02-02 19:19 ` [PATCH 3/7] mm: vmscan: kick flushers when we encounter dirty pages on the LRU fix Johannes Weiner
2017-02-02 19:19 ` [PATCH 4/7] mm: vmscan: remove old flusher wakeup from direct reclaim path Johannes Weiner
2017-02-02 19:19 ` [PATCH 5/7] mm: vmscan: only write dirty pages that the scanner has seen twice Johannes Weiner
2017-02-02 19:19 ` [PATCH 6/7] mm: vmscan: move dirty pages out of the way until they're flushed Johannes Weiner
2017-02-03 7:42 ` Hillf Danton
2017-02-03 15:15 ` Michal Hocko
2017-02-02 19:19 ` Johannes Weiner [this message]
2017-02-02 22:49 ` [PATCH 0/7] mm: vmscan: fix kswapd writeback regression v2 Andrew Morton
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