Messages in this thread | | | Date | Fri, 22 Mar 2019 13:30:25 +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 08:40:03PM -0400, Liang, Kan wrote: > > > On 3/21/2019 5:20 PM, Peter Zijlstra wrote: > > 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()? > > > > I think we have to reset both cpuc->pebs_data_cfg and > cpuc->pebs_record_size. Because pebs_update_adaptive_cfg() can return 0. > If so, adaptive_pebs_record_size_update() will not be called. The > cpuc->pebs_record_size still use the stale data, which may be wrong.
Oh, bugger.. I see.
> > > + > > > + 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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