linux-kernel - Re: [PATCH] mm: warn about allocations which stall for too long

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Message-ID: <31729f1f-c0da-29e4-5777-69446daab122@gmail.com>
Date:   Sat, 24 Sep 2016 23:19:04 +1000
From:   Balbir Singh <bsingharora@...il.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...e.de>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] mm: warn about allocations which stall for too long



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.