From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Fri, 16 Oct 2009 13:52:40 +0200 (CEST) Received: from mail-px0-f189.google.com ([209.85.216.189]:60152 "EHLO mail-px0-f189.google.com" rhost-flags-OK-OK-OK-OK) by ftp.linux-mips.org with ESMTP id S1493593AbZJPLwd (ORCPT ); Fri, 16 Oct 2009 13:52:33 +0200 Received: by pxi27 with SMTP id 27so1722139pxi.22 for ; Fri, 16 Oct 2009 04:52:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:date:from:to:cc:subject :message-id:references:mime-version:content-type:content-disposition :in-reply-to:user-agent; bh=r04+XZ5pc95a6TBKCpo6MfnbvRuHr3AOq7xkJtaXFD4=; b=KHD6XAfyzL2OrsOWW3vwTZ4g6njBFRVmXpsu3QRqYO40tbRcEnK8GyBfJG2xWOEWY6 SUzpeqGLPMTZoKJtEQER2unXLumi9r5NIMeecuQFflRCahkFqucPtoMfaBoj4HDIKiQt sVfyARsP5JtnosLbfJ62t2B8dLJaoO2RGcF6o= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=wYAQ38mZ1wLmu/bqqZsx5DUSFw9waVKwdgbt1hsy/tebUWr2Ga+2p5PbR973XGjs63 zavOQYqtA13l6wgzPekNQ648tPF/OZQqyCjTDjZadxI8xOZec5suAQCGzACMrzUcf6db Jz8xykb3nGaOiOazf7eMPJpXI8jsg09hygCC0= Received: by 10.114.50.17 with SMTP id x17mr1475471wax.168.1255693946314; Fri, 16 Oct 2009 04:52:26 -0700 (PDT) Received: from hack ([58.31.79.117]) by mx.google.com with ESMTPS id 23sm741154pzk.12.2009.10.16.04.52.19 (version=TLSv1/SSLv3 cipher=RC4-MD5); Fri, 16 Oct 2009 04:52:25 -0700 (PDT) Date: Fri, 16 Oct 2009 19:52:14 +0800 From: =?utf-8?Q?Am=C3=A9rico?= Wang To: Wu Zhangjin Cc: linux-kernel@vger.kernel.org, linux-mips , Ralf Baechle , Thomas Gleixner , Steven Rostedt , Ingo Molnar , Manuel Lauss , Atsushi Nemoto Subject: Re: [PATCH 1/2] tracing: convert trace_clock_local() as weak function Message-ID: <20091016115214.GA3159@hack> References: <4205779ae74d7c4144ee6cbf4e3f15f833646356.1255692619.git.wuzhangjin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4205779ae74d7c4144ee6cbf4e3f15f833646356.1255692619.git.wuzhangjin@gmail.com> User-Agent: Mutt/1.5.19 (2009-01-05) 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: 24366 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: xiyou.wangcong@gmail.com Precedence: bulk X-list: linux-mips On Fri, Oct 16, 2009 at 07:38:24PM +0800, Wu Zhangjin wrote: >trace_clock_local() is based on the arch-specific sched_clock(), in X86, >it is tsc(64bit) based, which can give very high precision(about 1ns >with 1GHz). but in MIPS, the sched_clock() is jiffies based, which can >give only 10ms precison with 1000 HZ. which is not enough for tracing, >especially for Real Time system. > >so, we need to implement a MIPS specific sched_clock() to get higher >precision. There is a tsc like clock counter register in MIPS, whose >frequency is half of the processor, so, if the cpu frequency is 800MHz, >the time precision reaches 2.5ns, which is very good for tracing, even >for Real Time system. > >but 'Cause it is only 32bit long, which will rollover quickly, so, such >a sched_clock() will bring with extra load, which is not good for the >whole system. so, we only need to implement a arch-specific >trace_clock_local() for tracing. as a preparation, we convert it as a >weak function. > >The MIPS specific trace_clock_local() is coming in the next patch. > >Signed-off-by: Wu Zhangjin >--- > kernel/trace/trace_clock.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > >diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c >index 20c5f92..a04dc18 100644 >--- a/kernel/trace/trace_clock.c >+++ b/kernel/trace/trace_clock.c >@@ -26,7 +26,7 @@ > * Useful for tracing that does not cross to other CPUs nor > * does it go through idle events. > */ >-u64 notrace trace_clock_local(void) >+u64 __attribute__((weak)) notrace trace_clock_local(void) We have __weak. > { > unsigned long flags; > u64 clock; >-- >1.6.2.1 > >-- >To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html >Please read the FAQ at http://www.tux.org/lkml/ -- Live like a child, think like the god.