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Date: Sat, 26 Feb 2011 07:43:39 +0100
From: Andrea Arcangeli <aarcange@...hat.com>
To: Arthur Marsh <arthur.marsh@...ernode.on.net>
Cc: Clemens Ladisch <cladisch@...glemail.com>,
alsa-user@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
Mel Gorman <mel@....ul.ie>
Subject: Re: [Alsa-user] new source of MIDI playback slow-down identified -
5a03b051ed87e72b959f32a86054e1142ac4cf55 thp: use compaction in kswapd for
GFP_ATOMIC order > 0
On Thu, Feb 24, 2011 at 02:54:05AM +0100, Andrea Arcangeli wrote:
> Ok so tomorrow I'll get all results on these 3 kernels (
> compaction-kswapd-3+compaction_alloc_lowlat-2 vs
> compaction-no-kswapd-3+compaction_alloc_lowlat-2 vs
> compaction_alloc_lowlat2) on network server load, where throughout is
> measured in addition to latency. Then we'll have a better picture to
Latency is still lowest with compaction-no-kswapd-3. compaction_alloc
still is at the top of the profiling with
compaction-kswapd-3+compaction_alloc_lowlat-2. However
compaction-kswapd-3 reduced the overhead somewhat but not enough to be
as fast as with compaction-no-kswapd-3 (even if much better than
before).
So we should apply compaction-no-kswapd-3 to 2.6.38 I think.
====
Subject: compaction: fix high compaction latencies and remove compaction-kswapd
From: Andrea Arcangeli <aarcange@...hat.com>
It's safer to stop calling compaction from kswapd as that creates too
high load during memory pressure that can't be offseted by the
improved performance of compound allocations. NOTE: this is not
related to THP (THP allocations uses __GFP_NO_KSWAPD), this is only
related to frequent and small order allocations that make kswapd go
wild with compaction.
Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
---
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -405,10 +423,7 @@ static int compact_finished(struct zone
return COMPACT_COMPLETE;
/* Compaction run is not finished if the watermark is not met */
- if (cc->compact_mode != COMPACT_MODE_KSWAPD)
- watermark = low_wmark_pages(zone);
- else
- watermark = high_wmark_pages(zone);
+ watermark = low_wmark_pages(zone);
watermark += (1 << cc->order);
if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
@@ -421,15 +436,6 @@ static int compact_finished(struct zone
if (cc->order == -1)
return COMPACT_CONTINUE;
- /*
- * Generating only one page of the right order is not enough
- * for kswapd, we must continue until we're above the high
- * watermark as a pool for high order GFP_ATOMIC allocations
- * too.
- */
- if (cc->compact_mode == COMPACT_MODE_KSWAPD)
- return COMPACT_CONTINUE;
-
/* Direct compactor: Is a suitable page free? */
for (order = cc->order; order < MAX_ORDER; order++) {
/* Job done if page is free of the right migratetype */
@@ -551,8 +557,7 @@ static int compact_zone(struct zone *zon
unsigned long compact_zone_order(struct zone *zone,
int order, gfp_t gfp_mask,
- bool sync,
- int compact_mode)
+ bool sync)
{
struct compact_control cc = {
.nr_freepages = 0,
@@ -561,7 +566,6 @@ unsigned long compact_zone_order(struct
.migratetype = allocflags_to_migratetype(gfp_mask),
.zone = zone,
.sync = sync,
- .compact_mode = compact_mode,
};
INIT_LIST_HEAD(&cc.freepages);
INIT_LIST_HEAD(&cc.migratepages);
@@ -607,8 +611,7 @@ unsigned long try_to_compact_pages(struc
nodemask) {
int status;
- status = compact_zone_order(zone, order, gfp_mask, sync,
- COMPACT_MODE_DIRECT_RECLAIM);
+ status = compact_zone_order(zone, order, gfp_mask, sync);
rc = max(status, rc);
/* If a normal allocation would succeed, stop compacting */
@@ -639,7 +642,6 @@ static int compact_node(int nid)
.nr_freepages = 0,
.nr_migratepages = 0,
.order = -1,
- .compact_mode = COMPACT_MODE_DIRECT_RECLAIM,
};
zone = &pgdat->node_zones[zoneid];
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -11,9 +11,6 @@
/* The full zone was compacted */
#define COMPACT_COMPLETE 3
-#define COMPACT_MODE_DIRECT_RECLAIM 0
-#define COMPACT_MODE_KSWAPD 1
-
#ifdef CONFIG_COMPACTION
extern int sysctl_compact_memory;
extern int sysctl_compaction_handler(struct ctl_table *table, int write,
@@ -28,8 +25,7 @@ extern unsigned long try_to_compact_page
bool sync);
extern unsigned long compaction_suitable(struct zone *zone, int order);
extern unsigned long compact_zone_order(struct zone *zone, int order,
- gfp_t gfp_mask, bool sync,
- int compact_mode);
+ gfp_t gfp_mask, bool sync);
/* Do not skip compaction more than 64 times */
#define COMPACT_MAX_DEFER_SHIFT 6
@@ -74,8 +70,7 @@ static inline unsigned long compaction_s
}
static inline unsigned long compact_zone_order(struct zone *zone, int order,
- gfp_t gfp_mask, bool sync,
- int compact_mode)
+ gfp_t gfp_mask, bool sync)
{
return COMPACT_CONTINUE;
}
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2385,7 +2385,6 @@ loop_again:
* cause too much scanning of the lower zones.
*/
for (i = 0; i <= end_zone; i++) {
- int compaction;
struct zone *zone = pgdat->node_zones + i;
int nr_slab;
unsigned long balance_gap;
@@ -2426,24 +2425,9 @@ loop_again:
sc.nr_reclaimed += reclaim_state->reclaimed_slab;
total_scanned += sc.nr_scanned;
- compaction = 0;
- if (order &&
- zone_watermark_ok(zone, 0,
- high_wmark_pages(zone),
- end_zone, 0) &&
- !zone_watermark_ok(zone, order,
- high_wmark_pages(zone),
- end_zone, 0)) {
- compact_zone_order(zone,
- order,
- sc.gfp_mask, false,
- COMPACT_MODE_KSWAPD);
- compaction = 1;
- }
-
if (zone->all_unreclaimable)
continue;
- if (!compaction && nr_slab == 0 &&
+ if (nr_slab == 0 &&
!zone_reclaimable(zone))
zone->all_unreclaimable = 1;
/*
--
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