Re: [patch 0/4] Port KVM-trace to tracepoints

[fche@redhat.com (Frank Ch. Eigler)]

Avi Kivity <avi@qumranet.com> writes:

> [...]
>> Have you considered using trace_mark() directly - eliminating the
>> KVM_TRACEN() middlemen?
> [...]
> Using trace_mark() directly -- looking at it, seems to fit the
> requirements exactly.  Should have looked at it earlier.  Is there a
> way to get a list of all markers?

>From kernel-space, I can't find just now an API for listing them, but
there probably is / could be one.

>From user-space, lttng tools can probably do it.  systemtap can too:
     % stap -l 'kernel.mark("*")'

You could prototype binary tracing thusly:
     % stap -e 'probe kernel.mark("kvm_foobar") { 
         printf("%4b%4b%4b", # three 4-byte ints
                cpu(), $arg1, $arg2)
       }'

> Perhaps the kvmtrace marker->relay integration should be made a marker
> feature, since there is nothing specific to kvm in it.

Right, I believe something like that is in the lttng patch suite.


- FChE