From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stratos Karafotis Subject: Re: [PATCH 3/7] cpufreq: intel_pstate: Add debugfs file stats Date: Tue, 10 Jun 2014 19:21:12 +0300 Message-ID: <53973078.6040907@semaphore.gr> References: <53962072.6010702@semaphore.gr> <53972883.7070707@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from sema.semaphore.gr ([78.46.194.137]:57407 "EHLO sema.semaphore.gr" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752945AbaFJQVQ (ORCPT ); Tue, 10 Jun 2014 12:21:16 -0400 In-Reply-To: <53972883.7070707@gmail.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Dirk Brandewie , "Rafael J. Wysocki" , Viresh Kumar , Dirk Brandewie Cc: "linux-pm@vger.kernel.org" , LKML On 10/06/2014 06:47 =CE=BC=CE=BC, Dirk Brandewie wrote: > On 06/09/2014 02:00 PM, Stratos Karafotis wrote: >> Add stats file in debugfs under driver's parent directory >> (pstate_snb) which counts the time in nsecs per requested >> P state and the number of times the specific state >> was requested. >> >> The file presents the statistics per logical CPU in the >> following format. The time is displayed in msecs: >> >=20 > NAK >=20 > This adds significantly to the memory footprint to gather information > that is available by post processing the perf tracepoint information. > The increase isn't horrible on single socket desktop processor machin= es > but gets big with server class machines. One vendor I have talked to= considers > a machine with 1024 cpus to be a SMALL machine. >=20 If I am not wrong the sizeof pstate_stat is 20B. On my CPU with 20 P st= ates, we need 400B per logical CPU (3200B total in my desktop) plus 64B for stat= s pointers. In your example this would need about 400KB - 500KB? Is it too much for 1024 a CPUs system? I think it's a useful piece of info that we can have it directly withou= t post processing tracepoint. Is it acceptable to conditionally compile it with a new CONFIG option? Thanks, Stratos