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Subject: Re: [PATCH] mm: warn about allocations which stall for too long
To: Dave Hansen <dave.hansen@intel.com>, Michal Hocko <mhocko@kernel.org>,
        linux-mm@kvack.org
References: <20160923081555.14645-1-mhocko@kernel.org>
 <57E56789.1070205@intel.com>
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>
From: Balbir Singh <bsingharora@gmail.com>
Message-ID: <31729f1f-c0da-29e4-5777-69446daab122@gmail.com>
Date: Sat, 24 Sep 2016 23:19:04 +1000
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On 24/09/16 03:34, Dave Hansen wrote:
> On 09/23/2016 01:15 AM, Michal Hocko wrote:
>> +	/* 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),
>> +				order, gfp_mask, &gfp_mask);
>> +		stall_timeout += 10 * HZ;
>> +		dump_stack();
>> +	}
> 
> This would make an awesome tracepoint.  There's probably still plenty of
> value to having it in dmesg, but the configurability of tracepoints is
> hard to beat.

An awesome tracepoint and a great place to trigger other tracepoints. With stall timeout
increasing every time, do we only care about the first instance when we exceeded stall_timeout?
Do we debug just that instance?

Balbir Singh.