From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prarit Bhargava Subject: Re: [PATCH 2/2] turbostat, add set_base_cpu() Date: Fri, 22 May 2015 18:30:18 -0400 Message-ID: <555FADFA.609@redhat.com> References: <1432296063-22185-1-git-send-email-prarit@redhat.com> <1432296063-22185-3-git-send-email-prarit@redhat.com> <1A7043D5F58CCB44A599DFD55ED4C9484688E5F2@fmsmsx115.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1A7043D5F58CCB44A599DFD55ED4C9484688E5F2@fmsmsx115.amr.corp.intel.com> Sender: linux-kernel-owner@vger.kernel.org To: "Brown, Len" Cc: "linux-kernel@vger.kernel.org" , "linux-pm@vger.kernel.org" , "Semin, Andrey" List-Id: linux-pm@vger.kernel.org On 05/22/2015 11:55 AM, Brown, Len wrote: >> +void set_base_cpu(void) >> +{ >> + int cpu; >> + >> + for (cpu = 0; cpu <= topo.max_cpu_num; ++cpu) { >> + if (cpu_is_not_present(cpu)) >> + continue; >> + base_cpu = cpu; >> + break; >> + } >> + >> + if (base_cpu == -1) >> + err(-ENODEV, "No valid cpus found"); >> +} > > > cpu0 hard-coding is indeed arbitrary. > However, so is this proposed replacement, base_cpu. > Either may not match where turbostat is currently running, > and thus could provoke unnecessary cross-calls to get there. > > I think it would be better to ask getcpu(2) where we are already running, > and simply use that one. I think we can call it once and cache it, > as you proposed, rather than multiple system calls. Any objection to sched_getcpu()? That way the code is simply base_cpu = sched_getcpu(); if (base_cpu == -1) err(-ENODEV, "No valid cpus found"); P. > > thanks, > -Len > > ps. patches to turbostat should go to linux-pm@vger.kernel.org > >