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RE: Proposed systemtap access to perfmon hardware
- From: "Stone, Joshua I" <joshua dot i dot stone at intel dot com>
- To: "William Cohen" <wcohen at redhat dot com>
- Cc: "SystemTAP" <systemtap at sources dot redhat dot com>, "Maynard Johnson" <maynardj at us dot ibm dot com>
- Date: Thu, 23 Mar 2006 09:08:58 -0800
- Subject: RE: Proposed systemtap access to perfmon hardware
William Cohen wrote:
> As far as when the performance counters are set up and torn down it
> seems like it would be most reasonable to set them up before the first
> probe begin action and tear them down after the last probe end action.
I agree
> This would mean for sampling would need to have it stop sampling if
> don't want any additional samples while doing the probe end action.
This should be gated for you by using the session_state. Begin probes
only run during STAP_SESSION_STARTING, normal probes (including permon
sampling) should only run during STAP_SESSION_RUNNING, and end probes
only run during STAP_SESSION_STOPPING. If a probe is entered during a
state that doesn't match what it expects, it just returns with out
taking any action.
Josh