linux-kernel - Re: [PATCH] perf tools: Fix bug for perf kvm report without guestmount.

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Date:	Sun, 08 Dec 2013 21:32:52 -0700
From:	David Ahern <dsahern@...il.com>
To:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
CC:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf tools: Fix bug for perf kvm report without guestmount.

On 12/9/13, 10:12 AM, Dongsheng Yang wrote:
> On 12/08/2013 10:42 PM, David Ahern wrote:
>> On 12/9/13, 8:20 AM, Dongsheng Yang wrote:
>>> How about introduce an option named --guestpid? Then we can make the
>>> usage of perf kvm
>>> more clear:
>>>      * perf kvm --guestkallsyms --guestmodules --guestpid
>>> [top|record|report]
>>>          This usage is for only one guest and will not resolve the
>>> symbols from other guests.
>>
>> If there is only 1 guest then there should not be a problem right? You
>> give perf a single guest kallsyms as the "default" and it works.
>> --guestpid adds no value in that case.
>
> Yes, if there is only one guest is running, "default" guest is "the"
> guest. Then with my patch in this thread applied, it works well.
>
> But consider this scenario, there are two guests are running, but we
> need to record-report one of them.
>
> --guestmount can achieve this request, but as a shortcut of guestmount,
> --guest{kallysms, modules} dose not
> support it well, right? So, I think we can discard the default guest,
> and use guestpid in record-report.

No.

Use cases:
1. one guest
--guestkallsyms and --guestmodules apply to default guest; user should 
supply files that apply to the one guest. Supplying any other kallsyms 
is just nonsense. *NO* other arguments are needed.

2. more than 1 VM, *ALL* VMs running the same kernel
--guestkallsyms and --guestmodules apply to default guest; user should 
supply files that apply to all of guests. No other arguments are needed.

3. more than 1 VM, VMs running different kernels. 1+ VMs running the 
same kernel
--guestmount allows user to supply files that apply to all of guests 
based on pid. --guestkallsyms/guestmodules is used for any guest not 
showing up in guestmount.

David

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