linux-kernel - Re: [PATCH v7 3/3] KVM: perf: kvm events analysis tool

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Message-ID: <20120913134541.GH10019@ghostprotocols.net>
Date:	Thu, 13 Sep 2012 06:45:42 -0700
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	David Ahern <dsahern@...il.com>
Cc:	Dong Hao <haodong@...ux.vnet.ibm.com>,
	xiaoguangrong@...ux.vnet.ibm.com, avi@...hat.com,
	mtosatti@...hat.com, Ingo Molnar <mingo@...nel.org>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v7 3/3] KVM: perf: kvm events analysis tool

Em Wed, Sep 12, 2012 at 10:56:44PM -0600, David Ahern escreveu:
> >>  static const char * const kvm_usage[] = {
> >>+    "perf kvm [<options>] {top|record|report|diff|buildid-list|stat}",

> >The usage for the report/record sub commands of stat is never shown. e.g.,
> >$ perf kvm stat
> >--> shows help for perf-stat

> >$ perf kvm
> >--> shows the above and perf-kvm's usage
> 
> [I deleted this thread, so having to reply to one of my responses.
> hopefully noone is unduly harmed by this.]
> 
> I've been using this command a bit lately -- especially on nested
> virtualization -- and I think the syntax is quirky - meaning wrong.
> In my case I always follow up a record with a report and end up
> using a shell script wrapper that combines the 2 and running it
> repeatedly. e.g.,
> 
>     $PERF kvm stat record -o $FILE -p $pid -- sleep $time
>     [ $? -eq 0 ] && $PERF --no-pager kvm  -i $FILE stat report
> 
> As my daughter likes to say - awkward.
> 
> That suggests what is really needed is a 'live' mode - a continual
> updating of the output like perf top, not a record and analyze later
> mode. Which does come back to why I responded to this email -- the
> syntax is klunky and awkward.
> 
> So, I spent a fair amount of time today implementing a live mode.
> And after a lot of swearing at the tracepoint processing code I

What kind of swearing? I'm working on 'perf test' entries for
tracepoints to make sure we don't regress on the perf/libtraceevent
junction, doing that as prep work for further simplifying tracepoint
tools like sched, kvm, kmem, etc.

> finally have it working. And the format extends easily (meaning <
> day and the next step) to a perf-based kvm_stat replacement. Example
> syntax is:
> 
>    perf kvm stat [-p <pid>|-a|...]
> 
> which defaults to an update delay of 1 second, and vmexit analysis.
> 
> The guts of the processing logic come from the existing kvm-events
> code. The changes focus on combining the record and report paths
> into one. The display needs some help (Arnaldo?), but it seems to
> work well.
> 
> I'd like to get opinions on what next? IMO, the record/report path
> should not get a foot hold from a backward compatibility perspective
> and having to maintain those options. I am willing to take the
> existing patches into git to maintain authorship and from there
> apply patches to make the live mode work - which includes a bit of
> refactoring of perf code (like the stats changes).
> 
> Before I march down this path, any objections, opinions, etc?

Can I see the code?

- Arnaldo
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