From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932497AbeCITKg (ORCPT ); Fri, 9 Mar 2018 14:10:36 -0500 Received: from mail-it0-f67.google.com ([209.85.214.67]:34372 "EHLO mail-it0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932183AbeCITKe (ORCPT ); Fri, 9 Mar 2018 14:10:34 -0500 X-Google-Smtp-Source: AG47ELs2phAuoOi227Tf5OB4L9e513bmLJAn0XqxeLhXnH+lYVYJb8VOWQUCP/nZp2s1/Rb+3WR75g== From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Fri, 9 Mar 2018 14:10:30 -0500 (EST) X-X-Sender: vince@macbook-air To: Peter Zijlstra cc: Vince Weaver , kan.liang@linux.intel.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org, eranian@google.com, acme@redhat.com, hpa@zytor.com, alexander.shishkin@linux.intel.com, mingo@kernel.org, jolsa@redhat.com, linux-tip-commits@vger.kernel.org Subject: Re: [tip:perf/core] perf/x86/intel: Disable userspace RDPMC usage for large PEBS In-Reply-To: <20180309174218.GB4064@hirez.programming.kicks-ass.net> Message-ID: References: <1518474035-21006-6-git-send-email-kan.liang@linux.intel.com> <20180309174218.GB4064@hirez.programming.kicks-ass.net> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 9 Mar 2018, Peter Zijlstra wrote: > On Fri, Mar 09, 2018 at 09:31:11AM -0500, Vince Weaver wrote: > > On Fri, 9 Mar 2018, tip-bot for Kan Liang wrote: > > > > > Commit-ID: 1af22eba248efe2de25658041a80a3d40fb3e92e > > > Gitweb: https://git.kernel.org/tip/1af22eba248efe2de25658041a80a3d40fb3e92e > > > Author: Kan Liang > > > AuthorDate: Mon, 12 Feb 2018 14:20:35 -0800 > > > Committer: Ingo Molnar > > > CommitDate: Fri, 9 Mar 2018 08:22:23 +0100 > > > > > > perf/x86/intel: Disable userspace RDPMC usage for large PEBS > > > > > > > > > So this whole commit log is about disabling RDPMC usage for "large PEBS" > > but the actual change disables RDPMC if "PERF_X86_EVENT_FREERUNNING" > > > > Either the commit log is really misleading, or else a poor name was chosen > > for this feature. > > Its the same thing, and yes that might want renaming I suppose. I apologize for noticing these things so late in the game, but I haven't had time to keep up with a full lkml feed recently so I only see these things once I'm CC'd on them. So to summarize this: rdpmc is only disabled on a per-event basis, and only if that event is doing multi-pebs sampling? If that's true, then I don't think I have an issue with this. We finally got rdpmc support in a released PAPI, and it is a massive improvement when self-monitoring (even moreso if KPTI is enabled) so I was just trying to make sure this wouldn't suddenly disable rdpmc out from under us. Vince