Re: [PATCH RFC 0/4]Porting Xentrace to kvm

[Avi Kivity <avi@qumranet.com>]

Jan Kiszka wrote:
> Avi Kivity wrote:
>   
>> Liu, Eric E wrote:
>>     
>>> Hi,
>>> The following patches port xentrace to kvm which is useful for
>>> performance tuning and debugging.
>>>
>>> It is designed to allow debugging traces of kvm to be generated on
>>> Up/Smp machines. Each trace entry is outputted in a trace ring buffer
>>> for per cpu which is mapped to userspace, and the userspace tools can
>>> analyze the data according to some formats definitions.
>>>
>>> Since we already have had debugfs_entries and some other kernel debug
>>> mechanism to use, does this kvmtrace make sense? Any comment is
>>> welcomed. 
>>>   
>>>       
>> This looks very useful.  While kvm_stat provides good data, this is much 
>> more in depth.
>>
>> The kernel already contains a method of transferring percpu data to 
>> userspace; see Documentation/filesystems/relay.txt.  It supports mmap() 
>> and read().  Please see if it is a good fit.
>>     
>
> I would also suggest to use the new kernel standard for instrumentation:
> trace_mark().
>
> This would also allow to reuse the trace points with other tracer and
> maybe even obsolete a separate transportation channel, e.g. when LTTng
> is once :-/ merged.
>   

Can one have markers automatically recorded?  Or do you need to connect 
the marker with a logging function?

If the latter, it's too difficult to use.

-- 
error compiling committee.c: too many arguments to function


-------------------------------------------------------------------------
This SF.net email is sponsored by: Microsoft
Defy all challenges. Microsoft(R) Visual Studio 2008.
http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/