From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 23 Nov 2009 10:01:45 +0100 (CET) Received: from mail-pw0-f45.google.com ([209.85.160.45]:63904 "EHLO mail-pw0-f45.google.com" rhost-flags-OK-OK-OK-OK) by ftp.linux-mips.org with ESMTP id S1492555AbZKWJBj (ORCPT ); Mon, 23 Nov 2009 10:01:39 +0100 Received: by pwi15 with SMTP id 15so3460512pwi.24 for ; Mon, 23 Nov 2009 01:01:31 -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=Ckx627iUuM2r2NAFJYzZZ+o/GGiUL/wc4iGzcSDdTlE=; b=YZmqhfbSFq4i1QhfT4dY7OJK+xChVBEJ+FbAb3+GX7o869YMYfU/B31LsHAoIqimeX k7+I3Yh/ulTqlIGy5ijLCUlYnfasMrj5QwLP76mxz4Rt+KnQ6ZFF2QCr/FuV7yCV9xlX io5JjNQO01Xq12f7LhoBIiG72voNtj21gs6ds= 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=xfSQEkoqP4MB3gKvQ6cYwcJmQ3ljG/v2MPpxDr+N3/iddoZsz714x4QmSfCEIlIWD0 aYlIXDuZXoWJC8chfJJKRjlYLvmTu3JbLHi/F96My3LHmxGVDAEpvfIrNUMZQMQ+t5Ro sqg9wx+qdZQX5H7EmEhUmCOERpw2tLoJzMDt0= Received: by 10.114.18.17 with SMTP id 17mr8338496war.131.1258966891210; Mon, 23 Nov 2009 01:01:31 -0800 (PST) Received: from ?172.16.2.101? ([222.92.8.142]) by mx.google.com with ESMTPS id 20sm2941862pzk.1.2009.11.23.01.01.25 (version=TLSv1/SSLv3 cipher=RC4-MD5); Mon, 23 Nov 2009 01:01:30 -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: Ingo Molnar Cc: Sergei Shtylyov , Ralf Baechle , Thomas Gleixner , linux-mips@linux-mips.org, Michal Simek In-Reply-To: <20091123084423.GB23635@elte.hu> References: <4B098AE4.6090804@ru.mvista.com> <1258938035.2411.6.camel@falcon.domain.org> <20091123084423.GB23635@elte.hu> Content-Type: text/plain; charset="UTF-8" Organization: DSLab, Lanzhou University, China Date: Mon, 23 Nov 2009 17:00:43 +0800 Message-ID: <1258966849.6088.0.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: 25051 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 Mon, 2009-11-23 at 09:44 +0100, Ingo Molnar wrote: > * Wu Zhangjin wrote: > > > 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. > > The proper solution would be what i suggested in my previous mail: to > put it into a separate .c file. It's easy as the code has its own > Kconfig value already. The only #ifdef is out of sight in a .h file. > Done, thanks! Regards, Wu Zhangjin