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* [PATCH 0/2] Reduce the amount of time compaction disables IRQs for V2
@ 2011-02-25 20:04 ` Mel Gorman
  0 siblings, 0 replies; 56+ messages in thread
From: Mel Gorman @ 2011-02-25 20:04 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Arthur Marsh, Clemens Ladisch, Andrea Arcangeli, Mel Gorman,
	Linux-MM, Linux Kernel Mailing List

Changelog since V1
  o Fix initialisation of isolated (Andrea)

The following two patches are aimed at reducing the amount of time IRQs are
disabled. It was reported by some ALSA people that transparent hugepages was
causing slowdowns on MIDI playback but I strongly suspect that compaction
running for smaller orders was also a factor. The theory was that IRQs
were being disabled for too long and sure enough, compaction was found to
be disabling IRQs for a long time. The patches reduce the length of time
IRQs are disabled when scanning for free pages and for pages to migrate.

It's late in the cycle but the IRQs disabled times are sufficiently bad
that it would be desirable to have these merged for 2.6.38 if possible.

 mm/compaction.c |   35 ++++++++++++++++++++++++++++++-----
 1 files changed, 30 insertions(+), 5 deletions(-)

-- 
1.7.2.3


^ permalink raw reply	[flat|nested] 56+ messages in thread
* Re: [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration
@ 2011-03-01 15:35 ` Minchan Kim
  0 siblings, 0 replies; 56+ messages in thread
From: Minchan Kim @ 2011-03-01 15:35 UTC (permalink / raw)
  To: KAMEZAWA Hiroyuki
  Cc: Mel Gorman, Andrea Arcangeli, Andrew Morton, Arthur Marsh,
	Clemens Ladisch, Linux-MM, Linux Kernel Mailing List

On Tue, Mar 01, 2011 at 01:49:25PM +0900, KAMEZAWA Hiroyuki wrote:
> On Tue, 1 Mar 2011 13:11:46 +0900
> Minchan Kim <minchan.kim@gmail.com> wrote:
> 
> > On Tue, Mar 01, 2011 at 08:42:09AM +0900, KAMEZAWA Hiroyuki wrote:
> > > On Mon, 28 Feb 2011 10:18:27 +0000
> > > Mel Gorman <mel@csn.ul.ie> wrote:
> > > 
> > > > > BTW, can't we drop disable_irq() from all lru_lock related codes ?
> > > > > 
> > > > 
> > > > I don't think so - at least not right now. Some LRU operations such as LRU
> > > > pagevec draining are run from IPI which is running from an interrupt so
> > > > minimally spin_lock_irq is necessary.
> > > > 
> > > 
> > > pagevec draining is done by workqueue(schedule_on_each_cpu()). 
> > > I think only racy case is just lru rotation after writeback.
> > 
> > put_page still need irq disable.
> > 
> 
> Aha..ok. put_page() removes a page from LRU via __page_cache_release().
> Then, we may need to remove a page from LRU under irq context.
> Hmm...

But as __page_cache_release's comment said, normally vm doesn't release page in
irq context. so it would be rare.
If we can remove it, could we change all of spin_lock_irqsave with spin_lock?
If it is right, I think it's very desirable to reduce irq latency.

How about this? It's totally a quick implementation and untested. 
I just want to hear opinions of you guys if the work is valuable or not before
going ahead.

== CUT_HERE ==

diff --git a/include/linux/mm.h b/include/linux/mm.h
index c71c487..5d17de6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1353,7 +1353,7 @@ extern void si_meminfo_node(struct sysinfo *val, int nid);
 extern int after_bootmem;
 
 extern void setup_per_cpu_pageset(void);
-
+extern void setup_per_cpu_defer_free_pages(void);
 extern void zone_pcp_update(struct zone *zone);
 
 /* nommu.c */
diff --git a/init/main.c b/init/main.c
index 3627bb3..9c35fad 100644
--- a/init/main.c
+++ b/init/main.c
@@ -583,6 +583,7 @@ asmlinkage void __init start_kernel(void)
 	kmemleak_init();
 	debug_objects_mem_init();
 	setup_per_cpu_pageset();
+	setup_per_cpu_defer_free_pages();
 	numa_policy_init();
 	if (late_time_init)
 		late_time_init();
diff --git a/mm/swap.c b/mm/swap.c
index 1b9e4eb..62a9f3b 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -37,10 +37,23 @@
 /* How many pages do we try to swap or page in/out together? */
 int page_cluster;
 
+/*
+ * This structure is to free pages which are deallocated
+ * by interrupt context for reducing irq disable time.
+ */
+#define DEFER_FREE_PAGES_THRESH_HOLD	32
+struct defer_free_pages_pcp {
+	struct page *next;
+	unsigned long count;
+	struct work_struct work;
+};
+
+static DEFINE_PER_CPU(struct defer_free_pages_pcp, defer_free_pages);
 static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
 static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
 static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
 
+static void __put_single_page(struct page *page);
 /*
  * This path almost never happens for VM activity - pages are normally
  * freed via pagevecs.  But it gets used by networking.
@@ -59,10 +72,76 @@ static void __page_cache_release(struct page *page)
 	}
 }
 
+void init_defer_free_pages(struct defer_free_pages_pcp *free_pages)
+{
+	free_pages->count = 0;
+	free_pages->next = NULL;
+}
+
+static void drain_cpu_defer_free_pages(int cpu)
+{
+	struct page *page;
+	struct defer_free_pages_pcp *free_pages = &per_cpu(defer_free_pages, cpu);
+	local_irq_disable();
+	while((page = free_pages->next)) {
+		free_pages->next = (struct page*)page_private(page);
+		__put_single_page(page);
+		free_pages->count--;
+	}
+	local_irq_enable();
+}
+
+static void defer_free_pages_drain(struct work_struct *dummy)
+{
+	drain_cpu_defer_free_pages(get_cpu());
+	put_cpu();
+}
+
+void __init setup_per_cpu_defer_free_pages(void)
+{
+	int cpu;
+	struct defer_free_pages_pcp *free_pages;
+
+	get_online_cpus();
+	for_each_online_cpu(cpu) {
+		free_pages = &per_cpu(defer_free_pages, cpu);
+		INIT_WORK(&free_pages->work, defer_free_pages_drain);
+		init_defer_free_pages(free_pages);
+	}
+	put_online_cpus();
+}
+
+static void defer_free(struct page *page, int cpu)
+{
+	struct defer_free_pages_pcp *free_pages = &per_cpu(defer_free_pages, cpu);
+
+	set_page_private(page, (unsigned long)free_pages->next);
+	free_pages->next = page;
+	free_pages->count++;
+
+	if (free_pages->count >= DEFER_FREE_PAGES_THRESH_HOLD) {
+		schedule_work_on(cpu, &free_pages->work);
+		flush_work(&free_pages->work);
+	}
+}
+
+static void __page_cache_release_defer(struct page *page)
+{
+	static int i = 0;
+	defer_free(page, get_cpu());
+	put_cpu();
+}
+
 static void __put_single_page(struct page *page)
 {
-	__page_cache_release(page);
-	free_hot_cold_page(page, 0);
+	if (in_irq())
+		__page_cache_release_defer(page);
+	else {
+		__page_cache_release(page);
+		free_hot_cold_page(page, 0);
+	}
 }
 
 static void __put_compound_page(struct page *page)


> 
> Thanks,
> -Kame
> 

-- 
Kind regards,
Minchan Kim

^ permalink raw reply related	[flat|nested] 56+ messages in thread
* [PATCH 0/2] Reduce the amount of time compaction disables IRQs for
@ 2011-02-25 18:00 Mel Gorman
  2011-02-25 18:00   ` Mel Gorman
  0 siblings, 1 reply; 56+ messages in thread
From: Mel Gorman @ 2011-02-25 18:00 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Arthur Marsh, Clemens Ladisch, Andrea Arcangeli, Mel Gorman,
	Linux-MM, Linux Kernel Mailing List

The following two patches are aimed at reducing the amount of time IRQs are
disabled. It was reported by some ALSA people that transparent hugepages was
causing slowdowns on MIDI playback but I strongly suspect that compaction
running for smaller orders was also a factor. The theory was that IRQs
were being disabled for too long and sure enough, compaction was found to
be disabling IRQs for a long time. The patches reduce the length of time
IRQs are disabled when scanning for free pages and for pages to migrate.

It's late in the cycle but the IRQs disabled times are sufficiently bad
that it would be desirable to have these merged for 2.6.38 if possible.

 mm/compaction.c |   35 ++++++++++++++++++++++++++++++-----
 1 files changed, 30 insertions(+), 5 deletions(-)

-- 
1.7.2.3


^ permalink raw reply	[flat|nested] 56+ messages in thread
end of thread, other threads:[~2011-03-01 22:57 UTC | newest]

Thread overview: 56+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-02-25 20:04 [PATCH 0/2] Reduce the amount of time compaction disables IRQs for V2 Mel Gorman
2011-02-25 20:04 ` Mel Gorman
2011-02-25 20:04 ` [PATCH 1/2] mm: compaction: Minimise the time IRQs are disabled while isolating free pages Mel Gorman
2011-02-25 20:04   ` Mel Gorman
2011-02-25 22:34   ` Johannes Weiner
2011-02-25 22:34     ` Johannes Weiner
2011-02-28  1:55   ` KAMEZAWA Hiroyuki
2011-02-28  1:55     ` KAMEZAWA Hiroyuki
2011-02-28 22:08   ` Minchan Kim
2011-02-28 22:08     ` Minchan Kim
2011-02-25 20:04 ` [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration Mel Gorman
2011-02-25 20:04   ` Mel Gorman
2011-02-25 22:32   ` Johannes Weiner
2011-02-25 22:32     ` Johannes Weiner
2011-02-26  0:16     ` Andrea Arcangeli
2011-02-26  0:16       ` Andrea Arcangeli
2011-02-28  2:17   ` KAMEZAWA Hiroyuki
2011-02-28  2:17     ` KAMEZAWA Hiroyuki
2011-02-28  5:48     ` Andrea Arcangeli
2011-02-28  5:48       ` Andrea Arcangeli
2011-02-28  5:54       ` KAMEZAWA Hiroyuki
2011-02-28  5:54         ` KAMEZAWA Hiroyuki
2011-02-28  9:28         ` Mel Gorman
2011-02-28  9:28           ` Mel Gorman
2011-02-28  9:42           ` KAMEZAWA Hiroyuki
2011-02-28  9:42             ` KAMEZAWA Hiroyuki
2011-02-28 10:18             ` Mel Gorman
2011-02-28 10:18               ` Mel Gorman
2011-02-28 23:42               ` KAMEZAWA Hiroyuki
2011-02-28 23:42                 ` KAMEZAWA Hiroyuki
2011-03-01  4:11                 ` Minchan Kim
2011-03-01  4:11                   ` Minchan Kim
2011-03-01  4:49                   ` KAMEZAWA Hiroyuki
2011-03-01  4:49                     ` KAMEZAWA Hiroyuki
2011-02-28 23:01   ` Minchan Kim
2011-02-28 23:01     ` Minchan Kim
2011-02-28 23:07     ` Andrea Arcangeli
2011-02-28 23:07       ` Andrea Arcangeli
2011-02-28 23:25       ` Minchan Kim
2011-02-28 23:25         ` Minchan Kim
2011-03-01 22:15   ` Andrew Morton
2011-03-01 22:15     ` Andrew Morton
2011-02-25 20:07 ` [PATCH 0/2] Reduce the amount of time compaction disables IRQs for V2 Andrea Arcangeli
2011-02-25 20:07   ` Andrea Arcangeli
  -- strict thread matches above, loose matches on Subject: below --
2011-03-01 15:35 [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration Minchan Kim
2011-03-01 15:35 ` Minchan Kim
2011-03-01 16:19 ` Andrea Arcangeli
2011-03-01 16:19   ` Andrea Arcangeli
2011-03-01 22:22   ` Minchan Kim
2011-03-01 22:22     ` Minchan Kim
2011-03-01 22:34     ` Andrew Morton
2011-03-01 22:34       ` Andrew Morton
2011-03-01 22:57       ` Minchan Kim
2011-03-01 22:57         ` Minchan Kim
2011-02-25 18:00 [PATCH 0/2] Reduce the amount of time compaction disables IRQs for Mel Gorman
2011-02-25 18:00 ` [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration Mel Gorman
2011-02-25 18:00   ` Mel Gorman

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