From: Janani Ravichandran <janani.rvchndrn@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Janani Ravichandran <janani.rvchndrn@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC] scripts: Include postprocessing script for memory allocation tracing
Date: Thu, 20 Oct 2016 18:10:37 -0500 [thread overview]
Message-ID: <4F0F918D-B98A-48EC-82ED-EE7D32F222EA@gmail.com> (raw)
In-Reply-To: <20161018131343.GJ12092@dhcp22.suse.cz>
Michal,
> On Oct 18, 2016, at 8:13 AM, Michal Hocko <mhocko@kernel.org> wrote:
>
>>
>
> yes, function_graph tracer will give you _some_ information but it will
> not have the context you are looking for, right? See the following
> example
>
> ------------------------------------------
> 0) x-www-b-22756 => x-termi-4083
> ------------------------------------------
>
> 0) | __alloc_pages_nodemask() {
> 0) | /* mm_page_alloc: page=ffffea000411b380 pfn=1066702 order=0 migratetype=0 gfp_flags=GFP_KERNEL */
> 0) 3.328 us | }
> 3) | __alloc_pages_nodemask() {
> 3) | /* mm_page_alloc: page=ffffea0008f1f6c0 pfn=2344923 order=0 migratetype=0 gfp_flags=GFP_KERNEL */
> 3) 1.011 us | }
> 0) | __alloc_pages_nodemask() {
> 0) | /* mm_page_alloc: page=ffffea000411b380 pfn=1066702 order=0 migratetype=0 gfp_flags=GFP_KERNEL */
> 0) 0.587 us | }
> 3) | __alloc_pages_nodemask() {
> 3) | /* mm_page_alloc: page=ffffea0008f1f6c0 pfn=2344923 order=0 migratetype=0 gfp_flags=GFP_KERNEL */
> 3) 1.125 us | }
>
> How do I know which process has performed those allocations? I know that
> CPU0 should be running x-termi-4083 but what is running on other CPUs?
>
> Let me explain my usecase I am very interested in. Say I that a usespace
> application is not performing well. I would like to see some statistics
> about memory allocations performed for that app - are there few outliers
> or the allocation stalls increase gradually? Where do we spend time during
> that allocation? Reclaim LRU pages? Compaction or the slab shrinkers?
>
> To answer those questions I need to track particular events (alocation,
> reclaim, compaction) to the process and know how long each step
> took. Maybe we can reconstruct something from the above output but it is
> a major PITA. If we either hard start/stop pairs for each step (which
> we already do have for reclaim, compaction AFAIR) then this is an easy
> scripting. Another option would be to have only a single tracepoint for
> each step with a timing information.
>
> See my point?
Yes, if we want to know what processes are running on what CPUs,
echo funcgraph-proc > trace_options in the tracing directory should give us
what we want.
The bash script which is part of this patch does this kind of setup for you.
As a result, the output you get is something like what you see here:
https://github.com/Jananiravichandran/Analyzing-tracepoints/blob/master/no_tp_no_threshold.txt
Does this answer your question? Let me know if otherwise.
Janani.
> --
> Michal Hocko
> SUSE Labs
next prev parent reply other threads:[~2016-10-20 23:10 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-11 22:24 [RFC] scripts: Include postprocessing script for memory allocation tracing Janani Ravichandran
2016-09-12 12:16 ` Michal Hocko
2016-09-13 18:04 ` Janani Ravichandran
2016-09-19 9:42 ` Michal Hocko
2016-09-22 15:30 ` Janani Ravichandran
2016-09-23 8:07 ` Michal Hocko
2016-10-06 12:00 ` Michal Hocko
2016-10-11 14:43 ` Janani Ravichandran
2016-10-15 23:31 ` Janani Ravichandran
2016-10-16 7:33 ` Michal Hocko
[not found] ` <CANnt6X=RpSnuxGXZfF6Qa5mJpzC8gL3wkKJi3tQMZJBZJVWF3w@mail.gmail.com>
[not found] ` <A6E7231A-54FF-4D5C-90F5-0A8C4126CFEA@gmail.com>
2016-10-18 13:13 ` Michal Hocko
2016-10-20 23:10 ` Janani Ravichandran [this message]
2016-10-21 7:08 ` Michal Hocko
2016-10-27 15:42 ` Janani Ravichandran
-- strict thread matches above, loose matches on Subject: below --
2016-08-19 11:38 Janani Ravichandran
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