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[14/14] skip readahead if the cgroup is congested

Message ID 20180629192542.26649-15-josef@toxicpanda.com (mailing list archive)
State New, archived
Headers show

Commit Message

Josef Bacik June 29, 2018, 7:25 p.m. UTC 
From: Josef Bacik <jbacik@fb.com>

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>
---
 mm/readahead.c | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Tejun Heo July 2, 2018, 9:13 p.m. UTC | #1 
On Fri, Jun 29, 2018 at 03:25:42PM -0400, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
> 
> 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>

Thanks.
diff mbox

Patch

diff --git a/mm/readahead.c b/mm/readahead.c
index 539bbb6c1fad..cda6b09e0a59 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"
 
@@ -500,6 +501,9 @@  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);
@@ -550,6 +554,9 @@  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);
 }