From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 23 Nov 2009 02:01:08 +0100 (CET) Received: from mail-pw0-f45.google.com ([209.85.160.45]:62105 "EHLO mail-pw0-f45.google.com" rhost-flags-OK-OK-OK-OK) by ftp.linux-mips.org with ESMTP id S1493101AbZKWBBC (ORCPT ); Mon, 23 Nov 2009 02:01:02 +0100 Received: by pwi15 with SMTP id 15so3249746pwi.24 for ; Sun, 22 Nov 2009 17:00:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:subject:from:reply-to:to:cc :in-reply-to:references:content-type:organization:date:message-id :mime-version:x-mailer:content-transfer-encoding; bh=cVObQYWNCb36UL1oxUgZZXNrF6wVE6ED6ylN18Xx+a0=; b=MJ2RWDwlwMl+46GrxWH4EJibJInk8gW/+Vz2VJhlmEmRxkVB2mQiGa2wghQCW8Z3O+ gqZvuxk3nq3gJH+e3rUW7pJ+PppTe6PoNHcE2o8ormp/ZxkG/DI9tFBGyMkks1n4MQAT GfFkrtNjByY5lLCBCLRyvlZ65m8iBvjDgo7Nk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:reply-to:to:cc:in-reply-to:references:content-type :organization:date:message-id:mime-version:x-mailer :content-transfer-encoding; b=QFy+5uJ4QOTUHj80FDUi/Uh2BMuGgM+SRkyLAPnuQCgQuTIj2C5x2ZssNomYhFrT3w A/HBWmgzxaiP0S9hhKmM2x42mivchR2vS5nh7f/8axdpS8JXzg8O0ThgHQaN+qpG9AoQ IIarqWiHbJio1RVawoFYsEwwr9U6cUZ6Bzml8= Received: by 10.115.101.30 with SMTP id d30mr7375750wam.175.1258938052159; Sun, 22 Nov 2009 17:00:52 -0800 (PST) Received: from ?172.16.2.101? ([222.92.8.142]) by mx.google.com with ESMTPS id 21sm2456809pxi.4.2009.11.22.17.00.48 (version=TLSv1/SSLv3 cipher=RC4-MD5); Sun, 22 Nov 2009 17:00:51 -0800 (PST) Subject: Re: [PATCH v3] MIPS: Add a high resolution sched_clock() via cnt32_to_63(). From: Wu Zhangjin Reply-To: wuzhangjin@gmail.com To: Sergei Shtylyov Cc: Ralf Baechle , Ingo Molnar , Thomas Gleixner , linux-mips@linux-mips.org, Michal Simek In-Reply-To: <4B098AE4.6090804@ru.mvista.com> References: <4B098AE4.6090804@ru.mvista.com> Content-Type: text/plain; charset="UTF-8" Organization: DSLab, Lanzhou University, China Date: Mon, 23 Nov 2009 09:00:35 +0800 Message-ID: <1258938035.2411.6.camel@falcon.domain.org> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 25042 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: wuzhangjin@gmail.com Precedence: bulk X-list: linux-mips On Sun, 2009-11-22 at 22:03 +0300, Sergei Shtylyov wrote: > Hello. > > Wu Zhangjin wrote: > > > From: Wu Zhangjin > > > > (This v3 revision incorporates with the feedbacks from Ingo, Ralf and Sergei.) > > > > This patch adds a cnt32_to_63() and MIPS c0 count based sched_clock(), > > which provides high resolution. and also, one new kernel option > > (HR_SCHED_CLOCK) is added to enable/disable this sched_clock(). > > > > Without it, the Ftrace for MIPS will give useless timestamp information. > > > > Because cnt32_to_63() needs to be called at least once per half period > > to work properly, Differ from the old version, this v2 revision set up a > > kernel timer to ensure the requirement of some MIPSs which have short c0 > > count period. > > > > Signed-off-by: Wu Zhangjin > > --- > > arch/mips/Kconfig | 18 ++++++++++++++ > > arch/mips/kernel/csrc-r4k.c | 55 +++++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 73 insertions(+), 0 deletions(-) > > > > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig > > index b342197..5ea55f5 100644 > > --- a/arch/mips/Kconfig > > +++ b/arch/mips/Kconfig > > @@ -1952,6 +1952,24 @@ config NR_CPUS > > source "kernel/time/Kconfig" > > > > # > > +# High Resolution sched_clock() Configuration > > +# > > + > > +config HR_SCHED_CLOCK > > + bool "High Resolution sched_clock()" > > + depends on CSRC_R4K > > + default n > > + help > > + This option enables the MIPS c0 count based high resolution > > + sched_clock(). > > + > > + If you need a ns precision timestamp, you are recommended to enable > > + this option. For example, If you are using the Ftrace subsystem to do > > + real time tracing, this option is needed. > > + > > + If unsure, disable it. > > + > > +# > > # Timer Interrupt Frequency Configuration > > # > > > > diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c > > index e95a3cd..e287f0d 100644 > > --- a/arch/mips/kernel/csrc-r4k.c > > +++ b/arch/mips/kernel/csrc-r4k.c > > @@ -10,6 +10,57 @@ > > > > #include > > > > +#ifdef CONFIG_HR_SCHED_CLOCK > > +#include > > +#include > > + > > +/* > > + * MIPS sched_clock implementation. > > + * > > + * because cnt32_to_63() needs to be called at least once per half period to > > + * work properly, and some of the MIPS frequency is high, perhaps a kernel > > + * timer is needed to be set up to ensure this requirement is always met. > > + * Please refer to arch/arm/plat-orion/time.c and include/linux/cnt32_to_63.h > > + */ > > +static unsigned long __read_mostly tclk2ns_scale; > > +static unsigned long __read_mostly tclk2ns_scale_factor; > > + > > +unsigned long long notrace sched_clock(void) > > +{ > > + unsigned long long v = cnt32_to_63(read_c0_count()); > > + return (v * tclk2ns_scale) >> tclk2ns_scale_factor; > > +} > > + > > +static struct timer_list cnt32_to_63_keepwarm_timer; > > + > > +static void cnt32_to_63_keepwarm(unsigned long data) > > +{ > > + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data)); > > + (void) sched_clock(); > > +} > > + > > +static void __init setup_sched_clock(struct clocksource *cs, unsigned long tclk) > > +{ > > + unsigned long long v; > > + unsigned long data; > > + > > + v = cs->mult; > > + /* > > + * We want an even value to automatically clear the top bit > > + * returned by cnt32_to_63() without an additional run time > > + * instruction. So if the LSB is 1 then round it up. > > + */ > > + if (v & 1) > > + v++; > > + tclk2ns_scale = v; > > + tclk2ns_scale_factor = cs->shift; > > + > > + data = 0x80000000 / tclk * HZ; > > + setup_timer(&cnt32_to_63_keepwarm_timer, cnt32_to_63_keepwarm, data); > > + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data)); > > +} > > +#endif /* !CONFIG_HR_SCHED_CLOCK */ > > + > > static cycle_t c0_hpt_read(struct clocksource *cs) > > { > > return read_c0_count(); > > @@ -32,6 +83,10 @@ int __init init_r4k_clocksource(void) > > > > clocksource_set_clock(&clocksource_mips, mips_hpt_frequency); > > > > +#ifdef CONFIG_HR_SCHED_CLOCK > > + setup_sched_clock(&clocksource_mips, mips_hpt_frequency); > > +#endif > > + > > > > According to CodingStyle #ifdef's in the code are frowned upon. I > suggest that you add an empty setup_sched_clock() definition under #else > above and have the call here without #ifdef. That's the preferred way of > doing such things... > Done, thanks! Wil resend it later.