[PATCH] PM / Hibernate: Feed the wathdog when creating snapshot

[PATCH] PM / Hibernate: Feed the wathdog when creating snapshot

[Chen Yu]

There is a problem that when counting the pages for creating
the hibernation snapshot will take significant amount of
time, especially on system with large memory. Since the counting
job is performed with irq disabled, this might lead to NMI lockup.
The following warning were found on a system with 1.5TB DRAM:

[ 1124.758184] Freezing user space processes ... (elapsed 0.002 seconds) done.
[ 1124.768721] OOM killer disabled.
[ 1124.847009] PM: Preallocating image memory...
[ 1139.392042] NMI watchdog: Watchdog detected hard LOCKUP on cpu 27
[ 1139.392076] CPU: 27 PID: 3128 Comm: systemd-sleep Not tainted 4.13.0-0.rc2.git0.1.fc27.x86_64 #1
[ 1139.392077] task: ffff9f01971ac000 task.stack: ffffb1a3f325c000
[ 1139.392083] RIP: 0010:memory_bm_find_bit+0xf4/0x100
[ 1139.392084] RSP: 0018:ffffb1a3f325fc20 EFLAGS: 00000006
[ 1139.392084] RAX: 0000000000000000 RBX: 0000000013b83000 RCX: ffff9fbe89caf000
[ 1139.392085] RDX: ffffb1a3f325fc30 RSI: 0000000000003200 RDI: ffff9fbeaffffe80
[ 1139.392085] RBP: ffffb1a3f325fc40 R08: 0000000013b80000 R09: ffff9fbe89c54878
[ 1139.392085] R10: ffffb1a3f325fc2c R11: 0000000013b83200 R12: 0000000000000400
[ 1139.392086] R13: fffffd552e0c0000 R14: ffff9fc1bffd31e0 R15: 0000000000000202
[ 1139.392086] FS:  00007f3189704180(0000) GS:ffff9fbec8ec0000(0000) knlGS:0000000000000000
[ 1139.392087] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1139.392087] CR2: 00000085da0f7398 CR3: 000001771cf9a000 CR4: 00000000007406e0
[ 1139.392088] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1139.392088] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 1139.392088] PKRU: 55555554
[ 1139.392089] Call Trace:
[ 1139.392092]  ? memory_bm_set_bit+0x29/0x60
[ 1139.392094]  swsusp_set_page_free+0x2b/0x30
[ 1139.392098]  mark_free_pages+0x147/0x1c0
[ 1139.392099]  count_data_pages+0x41/0xa0
[ 1139.392101]  hibernate_preallocate_memory+0x80/0x450
[ 1139.392102]  hibernation_snapshot+0x58/0x410
[ 1139.392103]  hibernate+0x17c/0x310
[ 1139.392104]  state_store+0xdf/0xf0
[ 1139.392107]  kobj_attr_store+0xf/0x20
[ 1139.392111]  sysfs_kf_write+0x37/0x40
[ 1139.392113]  kernfs_fop_write+0x11c/0x1a0
[ 1139.392117]  __vfs_write+0x37/0x170
[ 1139.392121]  ? handle_mm_fault+0xd8/0x230
[ 1139.392122]  vfs_write+0xb1/0x1a0
[ 1139.392123]  SyS_write+0x55/0xc0
[ 1139.392126]  entry_SYSCALL_64_fastpath+0x1a/0xa5
...
[ 1144.690405] done (allocated 6590003 pages)
[ 1144.694971] PM: Allocated 26360012 kbytes in 19.89 seconds (1325.28 MB/s)

It has taken nearly 20 seconds(2.10GHz CPU) thus the NMI lockup
was triggered. In case the timeout of the NMI watch dog has been
set to 1 second, a safe interval should be 6590003/20 = 320k pages
in theory. However there might also be some platforms running at a
lower frequency, so feed the watchdog every 100k pages.

Reported-by: Jan Filipcewicz <jan.filipcewicz@intel.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
---
 mm/page_alloc.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6d00f74..543726a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -66,6 +66,7 @@
 #include <linux/kthread.h>
 #include <linux/memcontrol.h>
 #include <linux/ftrace.h>
+#include <linux/nmi.h>
 
 #include <asm/sections.h>
 #include <asm/tlbflush.h>
@@ -2531,9 +2532,12 @@ void drain_all_pages(struct zone *zone)
 
 #ifdef CONFIG_HIBERNATION
 
+/* Touch watchdog for every WD_INTERVAL_PAGE pages. */
+#define WD_INTERVAL_PAGE	(100*1024)
+
 void mark_free_pages(struct zone *zone)
 {
-	unsigned long pfn, max_zone_pfn;
+	unsigned long pfn, max_zone_pfn, page_num = 0;
 	unsigned long flags;
 	unsigned int order, t;
 	struct page *page;
@@ -2548,6 +2552,9 @@ void mark_free_pages(struct zone *zone)
 		if (pfn_valid(pfn)) {
 			page = pfn_to_page(pfn);
 
+			if (!((page_num++) % WD_INTERVAL_PAGE))
+				touch_nmi_watchdog();
+
 			if (page_zone(page) != zone)
 				continue;
 
@@ -2561,8 +2568,11 @@ void mark_free_pages(struct zone *zone)
 			unsigned long i;
 
 			pfn = page_to_pfn(page);
-			for (i = 0; i < (1UL << order); i++)
+			for (i = 0; i < (1UL << order); i++) {
+				if (!((page_num++) % WD_INTERVAL_PAGE))
+					touch_nmi_watchdog();
 				swsusp_set_page_free(pfn_to_page(pfn + i));
+			}
 		}
 	}
 	spin_unlock_irqrestore(&zone->lock, flags);
-- 
2.7.4

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Re: [PATCH] PM / Hibernate: Feed the wathdog when creating snapshot

[Andrew Morton]

On Mon, 21 Aug 2017 23:08:18 +0800 Chen Yu <yu.c.chen@intel.com> wrote:

> There is a problem that when counting the pages for creating
> the hibernation snapshot will take significant amount of
> time, especially on system with large memory. Since the counting
> job is performed with irq disabled, this might lead to NMI lockup.
> The following warning were found on a system with 1.5TB DRAM:
> 
> ...
> 
> It has taken nearly 20 seconds(2.10GHz CPU) thus the NMI lockup
> was triggered. In case the timeout of the NMI watch dog has been
> set to 1 second, a safe interval should be 6590003/20 = 320k pages
> in theory. However there might also be some platforms running at a
> lower frequency, so feed the watchdog every 100k pages.
> 
> ...
>
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2531,9 +2532,12 @@ void drain_all_pages(struct zone *zone)
>  
>  #ifdef CONFIG_HIBERNATION
>  
> +/* Touch watchdog for every WD_INTERVAL_PAGE pages. */
> +#define WD_INTERVAL_PAGE	(100*1024)
> +
>  void mark_free_pages(struct zone *zone)
>  {
> -	unsigned long pfn, max_zone_pfn;
> +	unsigned long pfn, max_zone_pfn, page_num = 0;
>  	unsigned long flags;
>  	unsigned int order, t;
>  	struct page *page;
> @@ -2548,6 +2552,9 @@ void mark_free_pages(struct zone *zone)
>  		if (pfn_valid(pfn)) {
>  			page = pfn_to_page(pfn);
>  
> +			if (!((page_num++) % WD_INTERVAL_PAGE))
> +				touch_nmi_watchdog();
> +
>  			if (page_zone(page) != zone)
>  				continue;
>  
> @@ -2561,8 +2568,11 @@ void mark_free_pages(struct zone *zone)
>  			unsigned long i;
>  
>  			pfn = page_to_pfn(page);
> -			for (i = 0; i < (1UL << order); i++)
> +			for (i = 0; i < (1UL << order); i++) {
> +				if (!((page_num++) % WD_INTERVAL_PAGE))
> +					touch_nmi_watchdog();
>  				swsusp_set_page_free(pfn_to_page(pfn + i));
> +			}
>  		}
>  	}
>  	spin_unlock_irqrestore(&zone->lock, flags);

hm, is it really worth all the WD_INTERVAL_PAGE stuff? 
touch_nmi_watchdog() is pretty efficient and calling it once-per-page
may not have a measurable effect.

And if we're really concerned about the performance impact it would be
better to make WD_INTERVAL_PAGE a power of 2 (128*1024?) to avoid the
modulus operation.

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Re: [PATCH] PM / Hibernate: Feed the wathdog when creating snapshot

[Chen Yu]

Hi Andrew,
On Mon, Aug 21, 2017 at 01:26:00PM -0700, Andrew Morton wrote:
> On Mon, 21 Aug 2017 23:08:18 +0800 Chen Yu <yu.c.chen@intel.com> wrote:
> 
> > There is a problem that when counting the pages for creating
> > the hibernation snapshot will take significant amount of
> > time, especially on system with large memory. Since the counting
> > job is performed with irq disabled, this might lead to NMI lockup.
> > The following warning were found on a system with 1.5TB DRAM:
> > 
> > ...
> > 
> > It has taken nearly 20 seconds(2.10GHz CPU) thus the NMI lockup
> > was triggered. In case the timeout of the NMI watch dog has been
> > set to 1 second, a safe interval should be 6590003/20 = 320k pages
> > in theory. However there might also be some platforms running at a
> > lower frequency, so feed the watchdog every 100k pages.
> > 
> > ...
> >
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -2531,9 +2532,12 @@ void drain_all_pages(struct zone *zone)
> >  
> >  #ifdef CONFIG_HIBERNATION
> >  
> > +/* Touch watchdog for every WD_INTERVAL_PAGE pages. */
> > +#define WD_INTERVAL_PAGE	(100*1024)
> > +
> >  void mark_free_pages(struct zone *zone)
> >  {
> > -	unsigned long pfn, max_zone_pfn;
> > +	unsigned long pfn, max_zone_pfn, page_num = 0;
> >  	unsigned long flags;
> >  	unsigned int order, t;
> >  	struct page *page;
> > @@ -2548,6 +2552,9 @@ void mark_free_pages(struct zone *zone)
> >  		if (pfn_valid(pfn)) {
> >  			page = pfn_to_page(pfn);
> >  
> > +			if (!((page_num++) % WD_INTERVAL_PAGE))
> > +				touch_nmi_watchdog();
> > +
> >  			if (page_zone(page) != zone)
> >  				continue;
> >  
> > @@ -2561,8 +2568,11 @@ void mark_free_pages(struct zone *zone)
> >  			unsigned long i;
> >  
> >  			pfn = page_to_pfn(page);
> > -			for (i = 0; i < (1UL << order); i++)
> > +			for (i = 0; i < (1UL << order); i++) {
> > +				if (!((page_num++) % WD_INTERVAL_PAGE))
> > +					touch_nmi_watchdog();
> >  				swsusp_set_page_free(pfn_to_page(pfn + i));
> > +			}
> >  		}
> >  	}
> >  	spin_unlock_irqrestore(&zone->lock, flags);
> 
> hm, is it really worth all the WD_INTERVAL_PAGE stuff? 
> touch_nmi_watchdog() is pretty efficient and calling it once-per-page
> may not have a measurable effect.
>
We have version 1 of patch to feed the dog once-per-page. And we thought
it might look more elegant if we feed the dog every N pages.
> And if we're really concerned about the performance impact it would be
> better to make WD_INTERVAL_PAGE a power of 2 (128*1024?) to avoid the
> modulus operation.
> 
Ok, I'll change the interval to 128*1024 then.
Thanks,
	Yu

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