From: George Dunlap <george.dunlap@citrix.com>
To: Dario Faggioli <dario.faggioli@citrix.com>,
xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.com>,
George Dunlap <george.dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
Julien Grall <julien.grall@arm.com>,
Jan Beulich <jbeulich@suse.com>,
Jennifer Herbert <jennifer.herbert@citrix.com>,
Doug Goldstein <cardoe@cardoe.com>
Subject: Re: [PATCH 00/15] xen/tools: add tracing to various Xen subsystems
Date: Tue, 13 Jun 2017 17:34:31 +0100 [thread overview]
Message-ID: <8b16eb21-050a-a429-df34-4643f81ffe7f@citrix.com> (raw)
In-Reply-To: <149633614204.12814.14390287626133023934.stgit@Solace.fritz.box>
On 01/06/17 18:33, Dario Faggioli wrote:
> Hello,
>
> While chasing and dealing with bugs, over this last period, I've found myself
> augmenting Xen with quite a few new tracing capabilities, especially focusing
> on:
> - IRQ being disabled and (re)enabled (in addition to the already existing
> tracing of IRQ related activity that we have);
> - RCU;
> - softirqs (I think I sent a preliminary version of this, long ago, but can't
> be sure);
> - tasklets;
> - timers;
>
> And, apart from the first 4 patches (which are random, but still tracing
> related, of course, improvements), this is what this patch series does: it adds
> tracing to the Xen susystems listed above.
>
> That happens, one subsystem after another, in patches 6 to 15.
>
> Patch 5 deserves special mention. In fact, now that we have Kconfig, I thought
> it could be a nice thing to make it possible to select, at build config time,
> whether we want tracing or not, in the hypervisor (like, for instance, we do
> for performance counters).
>
> To be honest, my goal was to be able to compile tracing off, and run
> benchmarks, to assess how much of a overhead tracing introduces, but then I
> decided it was worth doing this properly, and now sending it. I am still
> running those benchmarks. Preliminary results seems to be showing that having
> tracing support in the hypervisor does not (when it's disabled, of course)
> introduce too much overhead. Still, I think it could be useful, to people that
> wants a very specificly tailored version of Xen (embedded, small footprint,
> etc.), to be able to rip it off nice and easily (e.g., like OpenXT guys did for
> schedulers).
>
> Of course, I will report here what I find, when benchmarks will finish running.
> (In the meantime, patch 5 has some data about .text section shrinking in its
> changelog.)
>
> I also thought, for similar reasons, that it would have been good to be able to
> also individually enable or disable the new tracing I'm introducing with this
> series. This potentially applies even to the tracing we already have in tree
> (e.g., one may want to have tracing compiled in, for everything except that for
> scheduling), and I'd be up for working on this. However, in this series, I am
> touching really hot paths (with the exception, maybe, of RCU), and so I think
> it is even more important to be able to disable tracing for them, for minimum
> overhead.
>
> For instance, the IRQ enabling and disabling tracing, I find it really really
> usable for understanding certain class of behavior, and, with some scripting
> and some more gnuplot "magic" (which I'll also share shortly) we can also use
> it to automatically measure and graph for how long interrupt are kept disabled,
> in various places within the hypervisor (Jennifer has done a similar analysis
> for XenServer, a while back). But it is very invasive, so you want to be able
> to turn it on and off.
> As said, I don't have all the result I need to present conclusions, but what I
> see in preliminary data is that, although the tracing we currently have in Xen
> is not too bad, performance wise, this new IRQs on/off tracing does have an
> impact on performance, just for being there in the code (i.e., even when it is
> there in the code but is *disabled*).
>
> Of course, all this fine grain control of tracing options is hidden under
> XEN_CONFIG_EXPERT, and all the new tracing is disabled by default.
>
> There is a branch with this series here:
> git://xenbits.xen.org/people/dariof/xen.git rel/tracing/xen-internals
> http://xenbits.xen.org/gitweb/?p=people/dariof/xen.git;a=shortlog;h=refs/heads/rel/tracing/xen-internals
>
> And Travis is happy about it:
> https://travis-ci.org/fdario/xen/builds/238421024
>
> Let me know what you think.
>
> Thanks and Regards,
> Dario
> ---
> Dario Faggioli (15):
> xen: in do_softirq() sample smp_processor_id() once and for all.
> xen: tracing: avoid checking tb_init_done multiple times.
> xen/tools: tracing: several improvements on IRQs tracing
> tools: xenalyze: fix dumping of PM_IDLE events.
> xen: make it possible to disable tracing in Kconfig.
> xen: trace IRQ enabling/disabling
> tools: tracing: handle IRQs on/off events in xentrace and xenalyze
> xen: trace RCU behavior
> tools: tracing: handle RCU events in xentrace and xenalyze
> xen: trace softirqs
> tools: tracing: handle RCU events in xentrace and xenalyze
> xen: trace tasklets
> tools: tracing: handle tasklets events in xentrace and xenalyze
> xen: trace timers
> tools: tracing: handle timers events in xentrace and xenalyze
Patches 10-15 look good to me too:
Acked-by: George Dunlap <george.dunlap@citrix.com>
-George
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prev parent reply other threads:[~2017-06-13 16:34 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-01 17:33 [PATCH 00/15] xen/tools: add tracing to various Xen subsystems Dario Faggioli
2017-06-01 17:33 ` [PATCH 01/15] xen: in do_softirq() sample smp_processor_id() once and for all Dario Faggioli
2017-06-07 14:38 ` Jan Beulich
2017-06-08 14:12 ` George Dunlap
2017-06-08 14:20 ` George Dunlap
2017-06-08 14:42 ` Jan Beulich
2017-06-01 17:33 ` [PATCH 02/15] xen: tracing: avoid checking tb_init_done multiple times Dario Faggioli
2017-06-01 17:53 ` Andrew Cooper
2017-06-01 23:08 ` Dario Faggioli
2017-06-07 14:46 ` Jan Beulich
2017-06-07 15:55 ` Dario Faggioli
2017-06-07 16:06 ` Jan Beulich
2017-06-08 14:34 ` George Dunlap
2017-06-08 14:37 ` George Dunlap
2017-06-01 17:33 ` [PATCH 03/15] xen/tools: tracing: several improvements on IRQs tracing Dario Faggioli
2017-06-01 18:02 ` Andrew Cooper
2017-06-01 23:12 ` Dario Faggioli
2017-06-07 15:05 ` Jan Beulich
2017-06-07 15:45 ` Dario Faggioli
2017-06-07 15:58 ` Jan Beulich
2017-06-08 14:53 ` George Dunlap
2017-06-08 15:34 ` Jan Beulich
2017-06-08 14:59 ` George Dunlap
2017-06-01 17:34 ` [PATCH 04/15] tools: xenalyze: fix dumping of PM_IDLE events Dario Faggioli
2017-06-08 15:06 ` George Dunlap
2017-06-01 17:34 ` [PATCH 05/15] xen: make it possible to disable tracing in Kconfig Dario Faggioli
2017-06-01 18:43 ` Andrew Cooper
2017-06-07 11:01 ` Julien Grall
2017-06-07 15:14 ` Jan Beulich
2017-06-08 15:16 ` George Dunlap
2017-06-08 15:35 ` Jan Beulich
2017-06-08 15:37 ` George Dunlap
2017-06-08 15:44 ` Jan Beulich
2017-06-08 15:17 ` George Dunlap
2017-06-01 17:34 ` [PATCH 06/15] xen: trace IRQ enabling/disabling Dario Faggioli
2017-06-01 19:08 ` Andrew Cooper
2017-06-01 23:42 ` Dario Faggioli
2017-06-08 15:51 ` George Dunlap
2017-06-08 16:05 ` Jan Beulich
2017-06-07 11:16 ` Julien Grall
2017-06-07 15:22 ` Dario Faggioli
2017-06-09 10:51 ` Julien Grall
2017-06-09 10:53 ` Julien Grall
2017-06-09 10:55 ` George Dunlap
2017-06-09 11:00 ` Julien Grall
2017-06-08 16:01 ` George Dunlap
2017-06-08 16:11 ` Dario Faggioli
2017-06-09 10:41 ` Jan Beulich
2017-06-01 17:34 ` [PATCH 07/15] tools: tracing: handle IRQs on/off events in xentrace and xenalyze Dario Faggioli
2017-06-13 15:58 ` George Dunlap
2017-06-01 17:34 ` [PATCH 08/15] xen: trace RCU behavior Dario Faggioli
2017-06-09 10:48 ` Jan Beulich
2017-06-13 16:05 ` George Dunlap
2017-06-01 17:34 ` [PATCH 09/15] tools: tracing: handle RCU events in xentrace and xenalyze Dario Faggioli
2017-06-13 16:12 ` George Dunlap
2017-06-01 17:34 ` [PATCH 10/15] xen: trace softirqs Dario Faggioli
2017-06-09 10:51 ` Jan Beulich
2017-06-01 17:34 ` [PATCH 11/15] tools: tracing: handle RCU events in xentrace and xenalyze Dario Faggioli
2017-06-01 17:35 ` [PATCH 12/15] xen: trace tasklets Dario Faggioli
2017-06-09 10:59 ` Jan Beulich
2017-06-09 11:17 ` Dario Faggioli
2017-06-09 11:29 ` Jan Beulich
2017-06-01 17:35 ` [PATCH 13/15] tools: tracing: handle tasklets events in xentrace and xenalyze Dario Faggioli
2017-06-01 17:35 ` [PATCH 14/15] xen: trace timers Dario Faggioli
2017-06-01 17:35 ` [PATCH 15/15] tools: tracing: handle timers events in xentrace and xenalyze Dario Faggioli
2017-06-07 14:13 ` [PATCH 00/15] xen/tools: add tracing to various Xen subsystems Konrad Rzeszutek Wilk
2017-06-08 16:45 ` Dario Faggioli
2017-06-13 16:34 ` George Dunlap [this message]
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