From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Kiszka <jan.kiszka@web.de>
Subject: Re: [PATCH RFC 0/4]Porting Xentrace to kvm
Date: Sun, 16 Mar 2008 16:45:09 +0100
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Cc: kvm-devel <kvm-devel@lists.sourceforge.net>,
	"Liu,  Eric E" <eric.e.liu@intel.com>
To: Avi Kivity <avi@qumranet.com>
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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.=20
>>  =20
>=20
> This looks very useful.  While kvm_stat provides good data, this is muc=
h=20
> more in depth.
>=20
> The kernel already contains a method of transferring percpu data to=20
> userspace; see Documentation/filesystems/relay.txt.  It supports mmap()=
=20
> 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.

Jan


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