Messages in this thread | | | Date | Thu, 21 Mar 2019 22:20:59 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH V2 04/23] perf/x86/intel: Support adaptive PEBSv4 |
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On Thu, Mar 21, 2019 at 01:56:44PM -0700, kan.liang@linux.intel.com wrote: > @@ -933,6 +1001,34 @@ pebs_update_state(bool needed_cb, struct cpu_hw_events *cpuc, struct pmu *pmu) > update = true; > } > > + /* > + * The PEBS record doesn't shrink on the del. Because to get > + * an accurate config needs to go through all the existing pebs events. > + * It's not necessary. > + * There is no harmful for a bigger PEBS record, except little > + * performance impacts. > + * Also, for most cases, the same pebs config is applied for all > + * pebs events. > + */ > + if (x86_pmu.intel_cap.pebs_baseline && add) { > + u64 pebs_data_cfg; > + > + /* Clear pebs_data_cfg and pebs_record_size for first PEBS. */ > + if (cpuc->n_pebs == 1) { > + cpuc->pebs_data_cfg = 0; > + cpuc->pebs_record_size = sizeof(struct pebs_basic); > + }
Argh, no. This is daft. The previous site was fine, it was just the pebs_record_size assignment I'm confused about.
Note how by setting ->pebs_data_cfs to 0, you force the below branch to true and call adaptive_pebs_record_size_update() ? So _why_ do you have to set pebs_record_size()?
> + > + pebs_data_cfg = pebs_update_adaptive_cfg(event); > + > + /* Update pebs_record_size if new event requires more data. */ > + if (pebs_data_cfg & ~cpuc->pebs_data_cfg) { > + cpuc->pebs_data_cfg |= pebs_data_cfg; > + adaptive_pebs_record_size_update(); > + update = true; > + } > + } > + > if (update) > pebs_update_threshold(cpuc); > }
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