On Fri, Sep 13, 2013 at 11:18:21PM -0700, Andi Kleen wrote: > tip-bot for Peter Zijlstra <tipbot@xxxxxxxxx> writes: > > + > > + at = (struct pebs_record_nhm *)(unsigned long)ds->pebs_buffer_base; > > + top = (struct pebs_record_nhm *)(unsigned long)ds->pebs_index; > > > > ds->pebs_index = ds->pebs_buffer_base; > > > > + n = (top - at) / x86_pmu.pebs_record_size; > > > This adds a full slow division to the PEBS hot path. > > Does not seem like a improvement to me. There already was an implicit division there, and sizeof(pebs_record_hsw) = 176, can it really optimize that constant division? I suppose we could go and introduce CONFIG_PERF_DEBUG and stuff sanity checks under that.. :/ -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|