From ca47e8c72ae141587cabf3dab693f6754d8c416b Mon Sep 17 00:00:00 2001
From: Josef Bacik <jbacik@fb.com>
Date: Tue, 3 Jul 2018 11:15:03 -0400
Subject: [PATCH] mm: skip readahead if the cgroup is congested
We noticed in testing we'd get pretty bad latency stalls under heavy
pressure because read ahead would try to do its thing while the cgroup
was under severe pressure. If we're under this much pressure we want to
do as little IO as possible so we can still make progress on real work
if we're a throttled cgroup, so just skip readahead if our group is
under pressure.
Signed-off-by: Josef Bacik <jbacik@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
mm/readahead.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/mm/readahead.c b/mm/readahead.c
index e273f0de33769..9f62b71511001 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -19,6 +19,7 @@
#include <linux/syscalls.h>
#include <linux/file.h>
#include <linux/mm_inline.h>
+#include <linux/blk-cgroup.h>
#include "internal.h"
@@ -505,6 +506,9 @@ void page_cache_sync_readahead(struct address_space *mapping,
if (!ra->ra_pages)
return;
+ if (blk_cgroup_congested())
+ return;
+
/* be dumb */
if (filp && (filp->f_mode & FMODE_RANDOM)) {
force_page_cache_readahead(mapping, filp, offset, req_size);
@@ -555,6 +559,9 @@ page_cache_async_readahead(struct address_space *mapping,
if (inode_read_congested(mapping->host))
return;
+ if (blk_cgroup_congested())
+ return;
+
/* do read-ahead */
ondemand_readahead(mapping, ra, filp, true, offset, req_size);
}
--
GitLab