* [PATCH] mm: vmscan: fix the page state calculation in too_many_isolated
@ 2015-01-13 11:07 Vinayak Menon
2015-01-13 16:09 ` Johannes Weiner
0 siblings, 1 reply; 3+ messages in thread
From: Vinayak Menon @ 2015-01-13 11:07 UTC (permalink / raw)
To: linux-mm, linux-kernel
Cc: akpm, hannes, vdavydov, mhocko, mgorman, minchan, Vinayak Menon
It is observed that sometimes multiple tasks get blocked for long
in the congestion_wait loop below, in shrink_inactive_list. This
is because of vm_stat values not being synced.
(__schedule) from [<c0a03328>]
(schedule_timeout) from [<c0a04940>]
(io_schedule_timeout) from [<c01d585c>]
(congestion_wait) from [<c01cc9d8>]
(shrink_inactive_list) from [<c01cd034>]
(shrink_zone) from [<c01cdd08>]
(try_to_free_pages) from [<c01c442c>]
(__alloc_pages_nodemask) from [<c01f1884>]
(new_slab) from [<c09fcf60>]
(__slab_alloc) from [<c01f1a6c>]
In one such instance, zone_page_state(zone, NR_ISOLATED_FILE)
had returned 14, zone_page_state(zone, NR_INACTIVE_FILE)
returned 92, and GFP_IOFS was set, and this resulted
in too_many_isolated returning true. But one of the CPU's
pageset vm_stat_diff had NR_ISOLATED_FILE as "-14". So the
actual isolated count was zero. As there weren't any more
updates to NR_ISOLATED_FILE and vmstat_update deffered work
had not been scheduled yet, 7 tasks were spinning in the
congestion wait loop for around 4 seconds, in the direct
reclaim path.
This patch uses zone_page_state_snapshot instead, but restricts
its usage to avoid performance penalty.
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
---
mm/vmscan.c | 68 ++++++++++++++++++++++++++++++++++++++++++++-----------------
1 file changed, 49 insertions(+), 19 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5e8772b..5e9667c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1392,6 +1392,44 @@ int isolate_lru_page(struct page *page)
return ret;
}
+static int __too_many_isolated(struct zone *zone, int file,
+ struct scan_control *sc, int safe)
+{
+ unsigned long inactive, isolated;
+
+ if (file) {
+ if (safe) {
+ inactive = zone_page_state_snapshot(zone,
+ NR_INACTIVE_FILE);
+ isolated = zone_page_state_snapshot(zone,
+ NR_ISOLATED_FILE);
+ } else {
+ inactive = zone_page_state(zone, NR_INACTIVE_FILE);
+ isolated = zone_page_state(zone, NR_ISOLATED_FILE);
+ }
+ } else {
+ if (safe) {
+ inactive = zone_page_state_snapshot(zone,
+ NR_INACTIVE_ANON);
+ isolated = zone_page_state_snapshot(zone,
+ NR_ISOLATED_ANON);
+ } else {
+ inactive = zone_page_state(zone, NR_INACTIVE_ANON);
+ isolated = zone_page_state(zone, NR_ISOLATED_ANON);
+ }
+ }
+
+ /*
+ * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
+ * won't get blocked by normal direct-reclaimers, forming a circular
+ * deadlock.
+ */
+ if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS)
+ inactive >>= 3;
+
+ return isolated > inactive;
+}
+
/*
* A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
* then get resheduled. When there are massive number of tasks doing page
@@ -1400,33 +1438,22 @@ int isolate_lru_page(struct page *page)
* unnecessary swapping, thrashing and OOM.
*/
static int too_many_isolated(struct zone *zone, int file,
- struct scan_control *sc)
+ struct scan_control *sc, int safe)
{
- unsigned long inactive, isolated;
-
if (current_is_kswapd())
return 0;
if (!global_reclaim(sc))
return 0;
- if (file) {
- inactive = zone_page_state(zone, NR_INACTIVE_FILE);
- isolated = zone_page_state(zone, NR_ISOLATED_FILE);
- } else {
- inactive = zone_page_state(zone, NR_INACTIVE_ANON);
- isolated = zone_page_state(zone, NR_ISOLATED_ANON);
+ if (unlikely(__too_many_isolated(zone, file, sc, 0))) {
+ if (safe)
+ return __too_many_isolated(zone, file, sc, safe);
+ else
+ return 1;
}
- /*
- * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
- * won't get blocked by normal direct-reclaimers, forming a circular
- * deadlock.
- */
- if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS)
- inactive >>= 3;
-
- return isolated > inactive;
+ return 0;
}
static noinline_for_stack void
@@ -1516,15 +1543,18 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
unsigned long nr_immediate = 0;
isolate_mode_t isolate_mode = 0;
int file = is_file_lru(lru);
+ int safe = 0;
struct zone *zone = lruvec_zone(lruvec);
struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
- while (unlikely(too_many_isolated(zone, file, sc))) {
+ while (unlikely(too_many_isolated(zone, file, sc, safe))) {
congestion_wait(BLK_RW_ASYNC, HZ/10);
/* We are about to die and free our memory. Return now. */
if (fatal_signal_pending(current))
return SWAP_CLUSTER_MAX;
+
+ safe = 1;
}
lru_add_drain();
--
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member of the Code Aurora Forum, hosted by The Linux Foundation
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm: vmscan: fix the page state calculation in too_many_isolated
2015-01-13 11:07 [PATCH] mm: vmscan: fix the page state calculation in too_many_isolated Vinayak Menon
@ 2015-01-13 16:09 ` Johannes Weiner
2015-01-14 11:27 ` Vinayak Menon
0 siblings, 1 reply; 3+ messages in thread
From: Johannes Weiner @ 2015-01-13 16:09 UTC (permalink / raw)
To: Vinayak Menon
Cc: linux-mm, linux-kernel, akpm, vdavydov, mhocko, mgorman, minchan
On Tue, Jan 13, 2015 at 04:37:27PM +0530, Vinayak Menon wrote:
> @@ -1392,6 +1392,44 @@ int isolate_lru_page(struct page *page)
> return ret;
> }
>
> +static int __too_many_isolated(struct zone *zone, int file,
> + struct scan_control *sc, int safe)
> +{
> + unsigned long inactive, isolated;
> +
> + if (file) {
> + if (safe) {
> + inactive = zone_page_state_snapshot(zone,
> + NR_INACTIVE_FILE);
> + isolated = zone_page_state_snapshot(zone,
> + NR_ISOLATED_FILE);
> + } else {
> + inactive = zone_page_state(zone, NR_INACTIVE_FILE);
> + isolated = zone_page_state(zone, NR_ISOLATED_FILE);
> + }
> + } else {
> + if (safe) {
> + inactive = zone_page_state_snapshot(zone,
> + NR_INACTIVE_ANON);
> + isolated = zone_page_state_snapshot(zone,
> + NR_ISOLATED_ANON);
> + } else {
> + inactive = zone_page_state(zone, NR_INACTIVE_ANON);
> + isolated = zone_page_state(zone, NR_ISOLATED_ANON);
> + }
> + }
if (safe) {
inactive = zone_page_state_snapshot(zone, NR_INACTIVE_ANON + 2*file)
isolated = zone_page_state_snapshot(zone, NR_ISOLATED_ANON + file)
} else {
inactive = zone_page_state(zone, NR_INACTIVE_ANON + 2*file)
isolated = zone_page_state(zone, NR_ISOLATED_ANON + file)
}
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm: vmscan: fix the page state calculation in too_many_isolated
2015-01-13 16:09 ` Johannes Weiner
@ 2015-01-14 11:27 ` Vinayak Menon
0 siblings, 0 replies; 3+ messages in thread
From: Vinayak Menon @ 2015-01-14 11:27 UTC (permalink / raw)
To: Johannes Weiner
Cc: linux-mm, linux-kernel, akpm, vdavydov, mhocko, mgorman, minchan
On 01/13/2015 09:39 PM, Johannes Weiner wrote:
> On Tue, Jan 13, 2015 at 04:37:27PM +0530, Vinayak Menon wrote:
>> @@ -1392,6 +1392,44 @@ int isolate_lru_page(struct page *page)
>> return ret;
>> }
>>
>> +static int __too_many_isolated(struct zone *zone, int file,
>> + struct scan_control *sc, int safe)
>> +{
>> + unsigned long inactive, isolated;
>> +
>> + if (file) {
>> + if (safe) {
>> + inactive = zone_page_state_snapshot(zone,
>> + NR_INACTIVE_FILE);
>> + isolated = zone_page_state_snapshot(zone,
>> + NR_ISOLATED_FILE);
>> + } else {
>> + inactive = zone_page_state(zone, NR_INACTIVE_FILE);
>> + isolated = zone_page_state(zone, NR_ISOLATED_FILE);
>> + }
>> + } else {
>> + if (safe) {
>> + inactive = zone_page_state_snapshot(zone,
>> + NR_INACTIVE_ANON);
>> + isolated = zone_page_state_snapshot(zone,
>> + NR_ISOLATED_ANON);
>> + } else {
>> + inactive = zone_page_state(zone, NR_INACTIVE_ANON);
>> + isolated = zone_page_state(zone, NR_ISOLATED_ANON);
>> + }
>> + }
>
> if (safe) {
> inactive = zone_page_state_snapshot(zone, NR_INACTIVE_ANON + 2*file)
> isolated = zone_page_state_snapshot(zone, NR_ISOLATED_ANON + file)
> } else {
> inactive = zone_page_state(zone, NR_INACTIVE_ANON + 2*file)
> isolated = zone_page_state(zone, NR_ISOLATED_ANON + file)
> }
>
Ok. Will change that.
--
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member of the Code Aurora Forum, hosted by The Linux Foundation
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^ permalink raw reply [flat|nested] 3+ messages in thread
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2015-01-13 16:09 ` Johannes Weiner
2015-01-14 11:27 ` Vinayak Menon
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