Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756137AbZKIPbr (ORCPT ); Mon, 9 Nov 2009 10:31:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756119AbZKIPbq (ORCPT ); Mon, 9 Nov 2009 10:31:46 -0500 Received: from mail-ew0-f207.google.com ([209.85.219.207]:39623 "EHLO mail-ew0-f207.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755969AbZKIPbn (ORCPT ); Mon, 9 Nov 2009 10:31:43 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=Q81VtJKfyRHM52RZaF5RWnWpYgNMlVNCBqTXN8j61agmCOfTH/3IiSJW1k9Wkn+0jb xQvRt5DKhzVnOgmXkc33XNB1otNaYssnhB0v29KUlyJs6IFd/osaJBMg/JpHhpGLxbdI FNv1/PMOtp01jWrCBtrwq+X4ZGJl5yKsRaW3w= From: Wu Zhangjin To: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org Cc: zhangfx@lemote.com, zhouqg@gmail.com, Wu Zhangjin , Ralf Baechle , rostedt@goodmis.org, Frederic Weisbecker , Ingo Molnar , Nicholas Mc Guire , David Daney , Richard Sandiford , Patrik Kluba , Thomas Gleixner , Michal Simek Subject: [PATCH v7 01/17] tracing: convert trace_clock_local() as weak function Date: Mon, 9 Nov 2009 23:31:18 +0800 Message-Id: <9dc81a7a9e5a292cccdf465c533a2b08d19d6021.1257779502.git.wuzhangjin@gmail.com> X-Mailer: git-send-email 1.6.2.1 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1883 Lines: 49 From: Wu Zhangjin 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 two patches. Acked-by: Frederic Weisbecker 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..06b8cd2 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 __weak notrace trace_clock_local(void) { 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/