From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ausmtp06.au.ibm.com (ausmtp06.au.ibm.com [202.81.18.155]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "ausmtp06.au.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTP id 45EEFDDE23 for ; Sun, 19 Aug 2007 18:56:26 +1000 (EST) Message-ID: <46C805B0.1000300@linux.vnet.ibm.com> Date: Sun, 19 Aug 2007 14:26:16 +0530 From: Balbir Singh MIME-Version: 1.0 To: Andrew Morton Subject: Re: [PATCH 1/2] Add scaled time to taskstats based process accounting References: <20070816070922.37B5370074@localhost.localdomain> <46C3FC41.4000609@linux.vnet.ibm.com> <19998.1187312981@neuling.org> <20070817115951.e1368a7d.akpm@linux-foundation.org> In-Reply-To: <20070817115951.e1368a7d.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Cc: Michael Neuling , Benjamin@ozlabs.org, Jay Lan , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Paul Mackerras Reply-To: balbir@linux.vnet.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Andrew Morton wrote: >> >> unsigned int rt_priority; >> - cputime_t utime, stime; >> + cputime_t utime, stime, utimescaled, stimescaled; > > Adding 8 or 16 bytes to the task_struct for all architectures for something > which only powerpc uses? > > Is there any prospect that other CPUs can use this? > Hi, Andrew, There is definitely the prospect for other architectures to use this feature x86 provides the APERF and MPERF model specific registers. The ratio of APERF to MPERF gives the current scaled load on the system (acpi-cpufreq, get_measured_perf()) I have been looking at exploiting this functionality for x-series, but ran into a problem; as per the specification, APERF and MPERF are to be reset to 0 upon reading them. As a result, I am still figuring out a good way to share the data amongst the ondemand governor and utimescaled statistics. I think for now, we can 1. Put utimescaled and stimescaled under an #ifdef for ARCH_POWERPC 2. Add utimescaled and stimescaled and add a big fat comment stating that work for other architectures is on it's way. In either case, I think the functionality is useful and can be exploited by other architectures. The powerpc port is complete and I think the implementation would provide a good reference for other implementations to follow. -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL