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From: "Hillf Danton" <hillf.zj@alibaba-inc.com>
To: "'Michal Hocko'" <mhocko@kernel.org>, <linux-mm@kvack.org>
Cc: "'Andrew Morton'" <akpm@linux-foundation.org>,
	"'Johannes Weiner'" <hannes@cmpxchg.org>,
	"'Mel Gorman'" <mgorman@suse.de>,
	"'Tetsuo Handa'" <penguin-kernel@I-love.SAKURA.ne.jp>,
	"'LKML'" <linux-kernel@vger.kernel.org>,
	"'Michal Hocko'" <mhocko@suse.com>
Subject: Re: [PATCH] mm: warn about allocations which stall for too long
Date: Fri, 23 Sep 2016 16:29:36 +0800	[thread overview]
Message-ID: <007901d21574$9ef82d60$dce88820$@alibaba-inc.com> (raw)
In-Reply-To: <20160923081555.14645-1-mhocko@kernel.org>

> 
> From: Michal Hocko <mhocko@suse.com>
> 
> Currently we do warn only about allocation failures but small
> allocations are basically nofail and they might loop in the page
> allocator for a long time.  Especially when the reclaim cannot make
> any progress - e.g. GFP_NOFS cannot invoke the oom killer and rely on
> a different context to make a forward progress in case there is a lot
> memory used by filesystems.
> 
> Give us at least a clue when something like this happens and warn about
> allocations which take more than 10s. Print the basic allocation context
> information along with the cumulative time spent in the allocation as
> well as the allocation stack. Repeat the warning after every 10 seconds so
> that we know that the problem is permanent rather than ephemeral.
> 
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
> 
> Hi,
> I am sending this as an RFC because I am not really sure what is the reasonable
> timeout when to warn. I went with 10s because that should be close to "for ever"
> from the user perspective. But maybe a shorter would be helpful as well?
> I didn't go with a tunable because I would rather not add a new one.
> 
> Thoughts? Ideas?
> 
>  mm/page_alloc.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 5155485057cb..d5faab8aa94d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3485,6 +3485,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  	enum compact_result compact_result;
>  	int compaction_retries = 0;
>  	int no_progress_loops = 0;
> +	unsigned long alloc_start = jiffies;
> +	unsigned int stall_timeout = 10 * HZ;
> 
>  	/*
>  	 * In the slowpath, we sanity check order to avoid ever trying to
> @@ -3659,6 +3661,15 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  	else
>  		no_progress_loops++;
> 
> +	/* Make sure we know about allocations which stall for too long */
> +	if (!(gfp_mask & __GFP_NOWARN) && time_after(jiffies, alloc_start + stall_timeout)) {
> +		pr_warn("%s: page alloction stalls for %ums: order:%u mode:%#x(%pGg)\n",
> +				current->comm, jiffies_to_msecs(jiffies-alloc_start),

Better if pid is also printed.
> +				order, gfp_mask, &gfp_mask);
> +		stall_timeout += 10 * HZ;

Alternatively	 alloc_start = jiffies;

> +		dump_stack();
> +	}
> +
>  	if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
>  				 did_some_progress > 0, no_progress_loops))
>  		goto retry;
> --
> 2.9.3
> 
thanks
Hillf

WARNING: multiple messages have this Message-ID
From: "Hillf Danton" <hillf.zj@alibaba-inc.com>
To: 'Michal Hocko' <mhocko@kernel.org>, linux-mm@kvack.org
Cc: 'Andrew Morton' <akpm@linux-foundation.org>,
	'Johannes Weiner' <hannes@cmpxchg.org>,
	'Mel Gorman' <mgorman@suse.de>,
	'Tetsuo Handa' <penguin-kernel@I-love.SAKURA.ne.jp>,
	'LKML' <linux-kernel@vger.kernel.org>,
	'Michal Hocko' <mhocko@suse.com>
Subject: Re: [PATCH] mm: warn about allocations which stall for too long
Date: Fri, 23 Sep 2016 16:29:36 +0800	[thread overview]
Message-ID: <007901d21574$9ef82d60$dce88820$@alibaba-inc.com> (raw)
In-Reply-To: <20160923081555.14645-1-mhocko@kernel.org>

> 
> From: Michal Hocko <mhocko@suse.com>
> 
> Currently we do warn only about allocation failures but small
> allocations are basically nofail and they might loop in the page
> allocator for a long time.  Especially when the reclaim cannot make
> any progress - e.g. GFP_NOFS cannot invoke the oom killer and rely on
> a different context to make a forward progress in case there is a lot
> memory used by filesystems.
> 
> Give us at least a clue when something like this happens and warn about
> allocations which take more than 10s. Print the basic allocation context
> information along with the cumulative time spent in the allocation as
> well as the allocation stack. Repeat the warning after every 10 seconds so
> that we know that the problem is permanent rather than ephemeral.
> 
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
> 
> Hi,
> I am sending this as an RFC because I am not really sure what is the reasonable
> timeout when to warn. I went with 10s because that should be close to "for ever"
> from the user perspective. But maybe a shorter would be helpful as well?
> I didn't go with a tunable because I would rather not add a new one.
> 
> Thoughts? Ideas?
> 
>  mm/page_alloc.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 5155485057cb..d5faab8aa94d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3485,6 +3485,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  	enum compact_result compact_result;
>  	int compaction_retries = 0;
>  	int no_progress_loops = 0;
> +	unsigned long alloc_start = jiffies;
> +	unsigned int stall_timeout = 10 * HZ;
> 
>  	/*
>  	 * In the slowpath, we sanity check order to avoid ever trying to
> @@ -3659,6 +3661,15 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  	else
>  		no_progress_loops++;
> 
> +	/* Make sure we know about allocations which stall for too long */
> +	if (!(gfp_mask & __GFP_NOWARN) && time_after(jiffies, alloc_start + stall_timeout)) {
> +		pr_warn("%s: page alloction stalls for %ums: order:%u mode:%#x(%pGg)\n",
> +				current->comm, jiffies_to_msecs(jiffies-alloc_start),

Better if pid is also printed.
> +				order, gfp_mask, &gfp_mask);
> +		stall_timeout += 10 * HZ;

Alternatively	 alloc_start = jiffies;

> +		dump_stack();
> +	}
> +
>  	if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
>  				 did_some_progress > 0, no_progress_loops))
>  		goto retry;
> --
> 2.9.3
> 
thanks
Hillf

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  reply	other threads:[~2016-09-23  8:35 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-23  8:15 Michal Hocko
2016-09-23  8:15 ` Michal Hocko
2016-09-23  8:29 ` Hillf Danton [this message]
2016-09-23  8:29   ` Hillf Danton
2016-09-23  8:32   ` Michal Hocko
2016-09-23  8:32     ` Michal Hocko
2016-09-23  8:44     ` Hillf Danton
2016-09-23  8:44       ` Hillf Danton
2016-09-23  9:15       ` Michal Hocko
2016-09-23  9:15         ` Michal Hocko
2016-09-23 14:36 ` Tetsuo Handa
2016-09-23 14:36   ` Tetsuo Handa
2016-09-23 15:02   ` Michal Hocko
2016-09-23 15:02     ` Michal Hocko
2016-09-24  3:00     ` Tetsuo Handa
2016-09-24  3:00       ` Tetsuo Handa
2016-09-26  8:17       ` Michal Hocko
2016-09-26  8:17         ` Michal Hocko
2016-09-27 12:57         ` Tetsuo Handa
2016-09-27 12:57           ` Tetsuo Handa
2016-09-29  8:48           ` Michal Hocko
2016-09-29  8:48             ` Michal Hocko
2016-09-23 17:34 ` Dave Hansen
2016-09-23 17:34   ` Dave Hansen
2016-09-24 13:19   ` Balbir Singh
2016-09-24 13:19     ` Balbir Singh
2016-09-26  8:13     ` Michal Hocko
2016-09-26  8:13       ` Michal Hocko
2016-09-26  8:12   ` Michal Hocko
2016-09-26  8:12     ` Michal Hocko
2016-09-29  8:44 ` [PATCH 0/2] " Michal Hocko
2016-09-29  8:44   ` Michal Hocko
2016-09-29  8:44   ` [PATCH 1/2] mm: consolidate warn_alloc_failed users Michal Hocko
2016-09-29  8:44     ` Michal Hocko
2016-09-29  9:23     ` Vlastimil Babka
2016-09-29  9:23       ` Vlastimil Babka
2016-09-29  8:44   ` [PATCH 2/2] mm: warn about allocations which stall for too long Michal Hocko
2016-09-29  8:44     ` Michal Hocko
2016-09-29  9:02     ` Tetsuo Handa
2016-09-29  9:02       ` Tetsuo Handa
2016-09-29  9:10       ` Michal Hocko
2016-09-29  9:10         ` Michal Hocko

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