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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>
This commit is contained in:
Josef Bacik 2018-07-03 11:15:03 -04:00 committed by Jens Axboe
parent b351f0c76c
commit ca47e8c72a
1 changed files with 7 additions and 0 deletions
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7
mm/readahead.c
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@ -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);
}