| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20110223163639.GM31195@random.random>
Date: Wed, 23 Feb 2011 17:36:39 +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 Wed, Feb 23, 2011 at 05:24:32PM +0100, Andrea Arcangeli wrote:
> On Wed, Feb 23, 2011 at 04:17:44AM +1030, Arthur Marsh wrote:
> > OK, these patches applied together against upstream didn't cause a crash
> > but I did observe:
> >
> > significant slowdowns of MIDI playback (moreso than in previous cases,
> > and with less than 20 Meg of swap file in use);
> >
> > kswapd0 sharing equal top place in CPU usage at times (e.g. 20 percent).
> >
> > If I should try only one of the patches or something else entirely,
> > please let me know.
>
> Yes, with irq off, schedule won't run and need_resched won't get set.
>
> So let's try this.
>
> In case this doesn't fix I definitely give it up with compaction in
> kswapd as GFP_ATOMIC will likely not get an huge benefit out of
> compaction anyway because 1) the allocations from GFP_ATOMIC are
> likely short lived, 2) the cost of the compaction scan loop +
> migration may be higher than the benefit we get from jumbo frames
>
> So if this doesn't fix it, I'll already post a definitive fix that
> removes compaction from kswapd (but leaves it enabled for direct
> reclaim for all order sizes including kernel stack). I already
> verified that this solves not just the midi latency issue but the
> other server benchmark that I'm dealing with. Then we can think at
> compaction+kswapd later for 2.6.39 but I think we need to close this
> kswapd issue in time for 2.6.38. So if the below isn't enough the next
> patch should be applied. I'll get those two patches tested in the
> server load too, and I'll let you know how the results are when it
> finishes.
>
> Please apply also the attached "kswapd-high-wmark" before the below
> one.
If the previous patch please test the below after the attached patch
(as usual). If the previous patch (last attempt for 2.6.38 to add
compaction in kswapd) fails this is the way to go for 2.6.38.
===
Subject: compaction: fix high compaction latencies and remove compaction-kswapd
From: Andrea Arcangeli <aarcange@...hat.com>
We need to proper spin_unlock_irq/cond_resched in the compaction loop to avoid
hurting latencies. We must also stop calling compaction from kswapd as that
creates too high load during memory pressure that can't be offseted by the
improved performance of hugepage allocations. NOTE: this is not related to THP
as all THP allocations uses __GFP_NO_KSWAPD, this is only related to usually
small order allocations like the kernel stack that make kswapd go wild with
compaction.
Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
---
mm/compaction.c | 40 +++++++++++++++++++++-------------------
1 file changed, 21 insertions(+), 19 deletions(-)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -271,9 +271,27 @@ static unsigned long isolate_migratepage
}
/* Time to isolate some pages for migration */
+ cond_resched();
spin_lock_irq(&zone->lru_lock);
for (; low_pfn < end_pfn; low_pfn++) {
struct page *page;
+ int unlocked = 0;
+
+ /* give a chance to irqs before checking need_resched() */
+ if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) {
+ spin_unlock_irq(&zone->lru_lock);
+ unlocked = 1;
+ }
+ if (need_resched() || spin_is_contended(&zone->lru_lock)) {
+ if (fatal_signal_pending(current))
+ break;
+ if (!unlocked)
+ spin_unlock_irq(&zone->lru_lock);
+ cond_resched();
+ spin_lock_irq(&zone->lru_lock);
+ } else if (unlocked)
+ spin_lock_irq(&zone->lru_lock);
+
if (!pfn_valid_within(low_pfn))
continue;
nr_scanned++;
@@ -397,10 +415,7 @@ 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))
@@ -413,15 +428,6 @@ 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 */
@@ -543,8 +549,7 @@ 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,
@@ -553,7 +558,6 @@ 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);
@@ -599,8 +603,7 @@ 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 */
@@ -631,7 +634,6 @@ 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];
View attachment "kswapd-high_wmark" of type "text/plain" (1854 bytes)
Powered by blists - more mailing lists