Messages in this thread | | | Subject | Re: [RFC PATCH 4/6] relay: add relay_reserve_cpu() | From | Tom Zanussi <> | Date | Thu, 05 Jul 2007 11:00:35 -0500 |
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On Tue, 2007-07-03 at 23:17 -0400, Mathieu Desnoyers wrote: > * Tom Zanussi (zanussi@us.ibm.com) wrote: > > This patch adds the ability to explicitly specify the per-cpu buffer > > to reserve space in. Needed for early DTI tracing. > > > > This should come with the ability to tell relay where the already > allocated static buffers are. Can you tell me a little more on why the > standard relay_reserve would not do the job? Is smp_processor_id() not > ready to output a sensible CPU id yet ? >
In the case of early tracing, the DTI code uses a global buffer and saves the cpuid along with each event. Later, when the relay channel is available, the relogging code wants to put each event in the appropriate per-cpu relay buffer. The standard relay_reserve() always uses the current cpuid, rather than the cpuid attached to the event, which is not what we want. relay_reserve_cpu() simply allows a cpuid other than the current one to be used.
Tom
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