Messages in this thread | | | Date | Tue, 16 Aug 2022 16:11:12 -0700 | From | Ira Weiny <> | Subject | Re: [RFC PATCH 1/9] cxl/mem: Implement Get Event Records command |
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On Tue, Aug 16, 2022 at 12:41:28PM -0400, Steven Rostedt wrote: > On Tue, 16 Aug 2022 12:39:58 -0400 > Steven Rostedt <rostedt@goodmis.org> wrote: > > > > + record_count = le16_to_cpu(payload.record_count); > > > + if (record_count > 0) > > > + trace_cxl_event(dev_name(cxlds->dev), type, > > > + &payload.record); > > > + > > > + if (payload.flags & CXL_GET_EVENT_FLAG_OVERFLOW) > > > + trace_cxl_event_overflow(dev_name(cxlds->dev), type, > > > + &payload); > > > > If you want to avoid the compare operations when the tracepoints are not > > enabled, you can add: > > > > if (trace_cxl_event_enabled()) { > > if (record_count > 0) > > trace_cxl_event(dev_name(cxlds->dev), type, > > &payload.record); > > } > > > > if (trace_cxl_event_overflow_enabled()) { > > if (payload.flags & CXL_GET_EVENT_FLAG_OVERFLOW) > > trace_cxl_event_overflow(dev_name(cxlds->dev), type, > > &payload); > > } > > > > Those "<tracepoint>_enabled()" functions are static branches. Which means > > when not enabled it's a nop that skips this code, and when either is > > enabled, it turns into a jump to the contents of the if block. > > Ignore this suggestion. I see in the second patch you add more logic to the > if condition.
Correct.
> Only use this suggestion if the logic is only for when the > tracepoint is enabled.
This could apply to the overflow trace. I think it is more likely that either all of these traces will be enabled or none.
So other than doing:
if (trace_cxl_event_enabled() || trace_cxl_event_overflow_enabled() || trace_cxl_gen_media_event() || <every event defined> ...) {
Is there a way to know if
/sys/kernel/tracing/events/cxl_events/enable
is != 0?
I feel like the real optimization will be to shut this entire functionality down if no one is listening.
Ira
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