linux-mips
[Top] [All Lists]

[PATCH -v6 01/13] tracing: convert trace_clock_local() as weak function

To: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
Subject: [PATCH -v6 01/13] tracing: convert trace_clock_local() as weak function
From: Wu Zhangjin <wuzhangjin@gmail.com>
Date: Mon, 26 Oct 2009 23:13:18 +0800
Cc: Wu Zhangjin <wuzhangjin@gmail.com>, Frederic Weisbecker <fweisbec@gmail.com>, rostedt@goodmis.org, Thomas Gleixner <tglx@linutronix.de>, Ralf Baechle <ralf@linux-mips.org>, Richard Sandiford <rdsandiford@googlemail.com>, Nicholas Mc Guire <der.herr@hofr.at>, David Daney <ddaney@caviumnetworks.com>, Adam Nemet <anemet@caviumnetworks.com>, Patrik Kluba <kpajko79@gmail.com>
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:from:to:cc:subject:date :message-id:x-mailer:in-reply-to:references:in-reply-to:references; bh=LT3AYB6XkTxNpHG8Gw+zUOC4kOO94rjbGYbttyFN5kg=; b=IJwOOQS2qV/UbdVpQx0iJJ6eYmMEX75m1DmdyaHIXIoHmPkWwQh326kxVCPbgnDdnN p2nqKdSBWL/3SeyU9I7eWLnRosRMHlF/kSJWOad52Mt+6q2l/4hG+JgA6hSoWJr2x5Iu ugeJTvQH6fbeQWFoIUOojxo9kgvNDy8fmxSPo=
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=sUvtVyl3pY7J82ZiMNmUiuuW8iTxg3IjwLUHYrF1z6FU0i/XK5YGhQcIE0MamLwStA sYQDQ255za37IyPAeM3xKe6P1vBcHOyAfIei4FXXbsuzvov71OyKYhyYS2pkbA8ju5OS kZrovf1pl9buSpZPP1NxVe1w6uS/tefSOUjCg=
In-reply-to: <cover.1256569489.git.wuzhangjin@gmail.com>
In-reply-to: <cover.1256569489.git.wuzhangjin@gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <cover.1256569489.git.wuzhangjin@gmail.com>
References: <cover.1256569489.git.wuzhangjin@gmail.com>
Sender: linux-mips-bounce@linux-mips.org
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.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
---
 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


<Prev in Thread] Current Thread [Next in Thread>