* Re: [patch] mm, compaction: periodically schedule when freeing pages
2013-09-04 23:25 [patch] mm, compaction: periodically schedule when freeing pages David Rientjes
@ 2013-09-04 23:58 ` Rik van Riel
2013-09-05 0:50 ` Wanpeng Li
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Rik van Riel @ 2013-09-04 23:58 UTC (permalink / raw)
To: David Rientjes
Cc: Andrew Morton, Mel Gorman, Minchan Kim, linux-kernel, linux-mm
On 09/04/2013 07:25 PM, David Rientjes wrote:
> We've been getting warnings about an excessive amount of time spent
> allocating pages for migration during memory compaction without
> scheduling. isolate_freepages_block() already periodically checks for
> contended locks or the need to schedule, but isolate_freepages() never
> does.
>
> When a zone is massively long and no suitable targets can be found, this
> iteration can be quite expensive without ever doing cond_resched().
>
> Check periodically for the need to reschedule while the compaction free
> scanner iterates.
>
> Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [patch] mm, compaction: periodically schedule when freeing pages
2013-09-04 23:25 [patch] mm, compaction: periodically schedule when freeing pages David Rientjes
2013-09-04 23:58 ` Rik van Riel
@ 2013-09-05 0:50 ` Wanpeng Li
2013-09-05 0:50 ` Wanpeng Li
2013-09-10 13:20 ` Mel Gorman
3 siblings, 0 replies; 5+ messages in thread
From: Wanpeng Li @ 2013-09-05 0:50 UTC (permalink / raw)
To: David Rientjes
Cc: Andrew Morton, Mel Gorman, Rik van Riel, Minchan Kim,
linux-kernel, linux-mm
On Wed, Sep 04, 2013 at 04:25:59PM -0700, David Rientjes wrote:
>We've been getting warnings about an excessive amount of time spent
>allocating pages for migration during memory compaction without
>scheduling. isolate_freepages_block() already periodically checks for
>contended locks or the need to schedule, but isolate_freepages() never
>does.
>
>When a zone is massively long and no suitable targets can be found, this
>iteration can be quite expensive without ever doing cond_resched().
>
>Check periodically for the need to reschedule while the compaction free
>scanner iterates.
>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
>Signed-off-by: David Rientjes <rientjes@google.com>
>---
> mm/compaction.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
>diff --git a/mm/compaction.c b/mm/compaction.c
>--- a/mm/compaction.c
>+++ b/mm/compaction.c
>@@ -677,6 +677,13 @@ static void isolate_freepages(struct zone *zone,
> pfn -= pageblock_nr_pages) {
> unsigned long isolated;
>
>+ /*
>+ * This can iterate a massively long zone without finding any
>+ * suitable migration targets, so periodically check if we need
>+ * to schedule.
>+ */
>+ cond_resched();
>+
> if (!pfn_valid(pfn))
> continue;
>
>
>--
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [patch] mm, compaction: periodically schedule when freeing pages
2013-09-04 23:25 [patch] mm, compaction: periodically schedule when freeing pages David Rientjes
2013-09-04 23:58 ` Rik van Riel
2013-09-05 0:50 ` Wanpeng Li
@ 2013-09-05 0:50 ` Wanpeng Li
2013-09-10 13:20 ` Mel Gorman
3 siblings, 0 replies; 5+ messages in thread
From: Wanpeng Li @ 2013-09-05 0:50 UTC (permalink / raw)
To: David Rientjes
Cc: Andrew Morton, Mel Gorman, Rik van Riel, Minchan Kim,
linux-kernel, linux-mm
On Wed, Sep 04, 2013 at 04:25:59PM -0700, David Rientjes wrote:
>We've been getting warnings about an excessive amount of time spent
>allocating pages for migration during memory compaction without
>scheduling. isolate_freepages_block() already periodically checks for
>contended locks or the need to schedule, but isolate_freepages() never
>does.
>
>When a zone is massively long and no suitable targets can be found, this
>iteration can be quite expensive without ever doing cond_resched().
>
>Check periodically for the need to reschedule while the compaction free
>scanner iterates.
>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
>Signed-off-by: David Rientjes <rientjes@google.com>
>---
> mm/compaction.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
>diff --git a/mm/compaction.c b/mm/compaction.c
>--- a/mm/compaction.c
>+++ b/mm/compaction.c
>@@ -677,6 +677,13 @@ static void isolate_freepages(struct zone *zone,
> pfn -= pageblock_nr_pages) {
> unsigned long isolated;
>
>+ /*
>+ * This can iterate a massively long zone without finding any
>+ * suitable migration targets, so periodically check if we need
>+ * to schedule.
>+ */
>+ cond_resched();
>+
> if (!pfn_valid(pfn))
> continue;
>
>
>--
>To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [patch] mm, compaction: periodically schedule when freeing pages
2013-09-04 23:25 [patch] mm, compaction: periodically schedule when freeing pages David Rientjes
` (2 preceding siblings ...)
2013-09-05 0:50 ` Wanpeng Li
@ 2013-09-10 13:20 ` Mel Gorman
3 siblings, 0 replies; 5+ messages in thread
From: Mel Gorman @ 2013-09-10 13:20 UTC (permalink / raw)
To: David Rientjes
Cc: Andrew Morton, Rik van Riel, Minchan Kim, linux-kernel, linux-mm
On Wed, Sep 04, 2013 at 04:25:59PM -0700, David Rientjes wrote:
> We've been getting warnings about an excessive amount of time spent
> allocating pages for migration during memory compaction without
> scheduling. isolate_freepages_block() already periodically checks for
> contended locks or the need to schedule, but isolate_freepages() never
> does.
>
> When a zone is massively long and no suitable targets can be found, this
> iteration can be quite expensive without ever doing cond_resched().
>
> Check periodically for the need to reschedule while the compaction free
> scanner iterates.
>
> Signed-off-by: David Rientjes <rientjes@google.com>
Ok, fair enough.
Acked-by: Mel Gorman <mgorman@suse.de>
However I'm curious. Do you know why the combined use of
compact_cached_free_pfn and pageblock skip bits is not enough for the scanner
to quickly find a pageblock that is suitable for isolate_freepages_block()?
Is the pageblock skip information getting cleared frequently by kswapd
or something?
--
Mel Gorman
SUSE Labs
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^ permalink raw reply [flat|nested] 5+ messages in thread