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

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Message-ID: <4F3C8E84.80905@gmail.com>
Date:	Wed, 15 Feb 2012 22:05:08 -0700
From:	David Ahern <dsahern@...il.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>
CC:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 3/3] KVM: perf: kvm events analysis tool

On 2/15/12 9:59 PM, Xiao Guangrong wrote:
>
>
> Okay, i will post the next version after collecting your new comments!
>
> Thanks for your time, David! :)
>

I had more comments, but got sidetracked and forgot to come back to 
this. I still haven't looked at the code yet, but some comments from 
testing:

1. The error message:
   Warning: Error: expected type 5 but read 4
   Warning: Error: expected type 5 but read 0
   Warning: unknown op '}'

is fixed by this patch which has not yet made its way into perf:
https://lkml.org/lkml/2011/9/4/41

The most recent request:
https://lkml.org/lkml/2012/2/8/479

Arnaldo: the patch still applies cleanly (but with an offset of -2 lines).

2. negatve testing:

perf kvm-events record -e kvm:* -p 2603 -- sleep 10

   Warning: Error: expected type 4 but read 7
   Warning: Error: expected type 5 but read 0
   Warning: failed to read event print fmt for kvm_apic
   Warning: Error: expected type 4 but read 7
   Warning: Error: expected type 5 but read 0
   Warning: failed to read event print fmt for kvm_inj_exception
   Fatal: bad op token {

If other kvm events are specified in the record line they appear to be 
silently ignored in the report in which case why allow the -e option to 
record?

3. What is happening for multiple VMs?

a. perf kvm-events report
data is collected for all VMs. What is displayed in the report? An
average for all VMs?

b. perf kvm-events report --vcpu 1
Does this given an average of all vcpu 1's?

Perhaps a -p option for the report to pull out events related to a 
single VM. Really this could be a generic option (to perf-report and 
perf-script as well) to only show/analyze events for the specified pid. 
ie., data is recorded for all VMs (or system wide for the regular 
perf-record) and you want to only consider events for a specific pid. 
e.g., in process_sample_event() skip event if event->ip.pid != 
report_pid (works for perf code because PERF_SAMPLE_TID attribute is 
always set).

David
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