From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35BCFC433F5 for ; Mon, 25 Apr 2022 15:45:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242978AbiDYPsu (ORCPT ); Mon, 25 Apr 2022 11:48:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53068 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242922AbiDYPst (ORCPT ); Mon, 25 Apr 2022 11:48:49 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7EE7E38DA8; Mon, 25 Apr 2022 08:45:45 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1650901543; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=aNGctTg/goq7Sq7mhvnKDj6DW5mQC3xi+xtGEu902nA=; b=4xclg1i0WuE8vnC7DCY7BDKUs0sa9ICOfob622p9cPKMqYo82Q+LT0u3zRDY1fN5eQmqpN PHyf9DbhGeTFbOjdXV/2jgPJvuJGITk74JvaK3LEd7Xfmq+ry9w4bEMkwt911F05SeQIDr 5+ojkalAzhgfFjtLJ+LYPV6/BCwtxEt81mgEsze8moUjbItQEXCsCaloJODdA6AGm16YCF GpYcPf7OuIcXTH2onSMRtlasOEAlUVX67kn6WzlH7ngXsBJTf1M0Y4/SPZt5K+4JeusTQv VLiBXEjmlsKuzYJaByi8ZHSEOqbPoYeKrMomPenDjMViVLVytvjvI5ljN/ebdA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1650901543; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=aNGctTg/goq7Sq7mhvnKDj6DW5mQC3xi+xtGEu902nA=; b=0pVlce+Q0osyO+0+0QOLt0JFlGwYK41Pr49WOEDLlNVNHac4paS0C7dge9bywRCmYoneCP RLdUK+tUk8BxS5AQ== To: Doug Smythies , "'Rafael J. Wysocki'" Cc: 'the arch/x86 maintainers' , "'Rafael J. Wysocki'" , 'Linux PM' , 'Eric Dumazet' , "'Paul E. McKenney'" , 'LKML' , Doug Smythies Subject: RE: [patch 00/10] x86/cpu: Consolidate APERF/MPERF code In-Reply-To: <005501d85503$3b00ca40$b1025ec0$@telus.net> References: <20220415133356.179706384@linutronix.de> <005001d85413$75e5dce0$61b196a0$@telus.net> <87bkwwvkwa.ffs@tglx> <005501d85503$3b00ca40$b1025ec0$@telus.net> Date: Mon, 25 Apr 2022 17:45:42 +0200 Message-ID: <87pml5180p.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Wed, Apr 20 2022 at 15:08, Doug Smythies wrote: > On 2022.04.19 14:11 Thomas Gleixner wrote: >>> That's because after the changes in this series scaling_cur_freq >>> returns 0 if the given CPU is idle. >> >> Which is sensible IMO as there is really no point in waking an idle CPU >> just to read those MSRs, then wait 20ms wake it up again to read those >> MSRs again. > > I totally agree. > It is the inconsistency for what is displayed as a function of driver/governor > that is my concern. Raphael suggested to move the show_cpuinfo() logic into the a/mperf code. See below. Thanks, tglx --- Subject: x86/aperfmperf: Integrate the fallback code from show_cpuinfo() From: Thomas Gleixner Date: Mon, 25 Apr 2022 15:19:29 +0200 Due to the avoidance of IPIs to idle CPUs arch_freq_get_on_cpu() can return 0 when the last sample was too long ago. show_cpuinfo() has a fallback to cpufreq_quick_get() and if that fails to return cpu_khz, but the readout code for the per CPU scaling frequency in sysfs does not. Move that fallback into arch_freq_get_on_cpu() so the behaviour is the same when reading /proc/cpuinfo and /sys/..../cur_scaling_freq. Suggested-by: "Rafael J. Wysocki" Signed-off-by: Thomas Gleixner --- arch/x86/kernel/cpu/aperfmperf.c | 10 +++++++--- arch/x86/kernel/cpu/proc.c | 7 +------ 2 files changed, 8 insertions(+), 9 deletions(-) --- a/arch/x86/kernel/cpu/aperfmperf.c +++ b/arch/x86/kernel/cpu/aperfmperf.c @@ -405,12 +405,12 @@ void arch_scale_freq_tick(void) unsigned int arch_freq_get_on_cpu(int cpu) { struct aperfmperf *s = per_cpu_ptr(&cpu_samples, cpu); + unsigned int seq, freq; unsigned long last; - unsigned int seq; u64 acnt, mcnt; if (!cpu_feature_enabled(X86_FEATURE_APERFMPERF)) - return 0; + goto fallback; do { seq = raw_read_seqcount_begin(&s->seq); @@ -424,9 +424,13 @@ unsigned int arch_freq_get_on_cpu(int cp * which covers idle and NOHZ full CPUs. */ if (!mcnt || (jiffies - last) > MAX_SAMPLE_AGE) - return 0; + goto fallback; return div64_u64((cpu_khz * acnt), mcnt); + +fallback: + freq = cpufreq_quick_get(cpu); + return freq ? freq : cpu_khz; } static int __init bp_init_aperfmperf(void) --- a/arch/x86/kernel/cpu/proc.c +++ b/arch/x86/kernel/cpu/proc.c @@ -86,12 +86,7 @@ static int show_cpuinfo(struct seq_file if (cpu_has(c, X86_FEATURE_TSC)) { unsigned int freq = arch_freq_get_on_cpu(cpu); - if (!freq) - freq = cpufreq_quick_get(cpu); - if (!freq) - freq = cpu_khz; - seq_printf(m, "cpu MHz\t\t: %u.%03u\n", - freq / 1000, (freq % 1000)); + seq_printf(m, "cpu MHz\t\t: %u.%03u\n", freq / 1000, (freq % 1000)); } /* Cache size */