Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1491135

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

Show all headers | View raw

On Fri 23-09-16 10:34:01, 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.

Currently we only have trace_mm_page_alloc in __alloc_pages_nodemask. I
think we want to add another one to mark the beginning of the allocation
so that we can track allocation latencies per allocation context and
ideally drop them down into sources - congestion waits, reclaim path,
slab reclaim etc. Janani Ravichandran is working on a script to do that
http://lkml.kernel.org/r/20160911222411.GA2854@janani-Inspiron-3521

But this sounds a bit orthogonal to my proposal here because I would
really like to warn unconditionally when an allocation stalls for
unreasonably long. Tracepoints are not an ideal tool for that because
you have to start collecting tracing output before this situations
happen. Moreover in my experience I often had to replace my local
debugging trace_printks by regular printks because the prior ones just
got lost under a heavy memory pressure.
-- 
Michal Hocko
SUSE Labs

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Re: [PATCH] mm: warn about allocations which stall for too long Dave Hansen <dave.hansen@intel.com> - 2016-09-23 19:40 +0200
  Re: [PATCH] mm: warn about allocations which stall for too long Balbir Singh <bsingharora@gmail.com> - 2016-09-24 15:20 +0200
    Re: [PATCH] mm: warn about allocations which stall for too long Michal Hocko <mhocko@kernel.org> - 2016-09-26 10:20 +0200
  Re: [PATCH] mm: warn about allocations which stall for too long Michal Hocko <mhocko@kernel.org> - 2016-09-26 10:20 +0200

csiph-web