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| author | Alex Shi <alex.shi@intel.com> | 2011-10-31 17:08:45 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-08-01 12:27:17 -0700 |
| commit | 9203b3fa57cc16bf1ad1be7c64b01b5e45cc6151 (patch) | |
| tree | f8a847fbadb5cfc577024f5634d5943a7af2bfa2 /mm | |
| parent | 5d62e5ca429b85ecadaa5042bdb1d8b88d4bfe80 (diff) | |
| download | linux-rt-9203b3fa57cc16bf1ad1be7c64b01b5e45cc6151.tar.gz | |
kswapd: assign new_order and new_classzone_idx after wakeup in sleeping
commit f0dfcde099453aa4c0dc42473828d15a6d492936 upstream.
Stable note: Fixes https://bugzilla.redhat.com/show_bug.cgi?id=712019. This
patch reduces kswapd CPU usage.
There 2 places to read pgdat in kswapd. One is return from a successful
balance, another is waked up from kswapd sleeping. The new_order and
new_classzone_idx represent the balance input order and classzone_idx.
But current new_order and new_classzone_idx are not assigned after
kswapd_try_to_sleep(), that will cause a bug in the following scenario.
1: after a successful balance, kswapd goes to sleep, and new_order = 0;
new_classzone_idx = __MAX_NR_ZONES - 1;
2: kswapd waked up with order = 3 and classzone_idx = ZONE_NORMAL
3: in the balance_pgdat() running, a new balance wakeup happened with
order = 5, and classzone_idx = ZONE_NORMAL
4: the first wakeup(order = 3) finished successufly, return order = 3
but, the new_order is still 0, so, this balancing will be treated as a
failed balance. And then the second tighter balancing will be missed.
So, to avoid the above problem, the new_order and new_classzone_idx need
to be assigned for later successful comparison.
Signed-off-by: Alex Shi <alex.shi@intel.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Tested-by: Pádraig Brady <P@draigBrady.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/vmscan.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 5cc0f92eda3e..870cbcfc328a 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2908,6 +2908,8 @@ static int kswapd(void *p) balanced_classzone_idx); order = pgdat->kswapd_max_order; classzone_idx = pgdat->classzone_idx; + new_order = order; + new_classzone_idx = classzone_idx; pgdat->kswapd_max_order = 0; pgdat->classzone_idx = pgdat->nr_zones - 1; } |