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Re: [PATCH v5] MIPS: Add a high resolution sched_clock() via cnt32_to_63

To: Wu Zhangjin <wuzhangjin@gmail.com>
Subject: Re: [PATCH v5] MIPS: Add a high resolution sched_clock() via cnt32_to_63().
From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Date: Mon, 23 Nov 2009 16:11:39 +0300
Cc: Ralf Baechle <ralf@linux-mips.org>, Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>, linux-mips@linux-mips.org, Michal Simek <monstr@monstr.eu>
In-reply-to: <39b95d02b37cd75d275b231c31abb00aefda9078.1258972025.git.wuzhangjin@gmail.com>
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Hello.

Wu Zhangjin wrote:

From: Wu Zhangjin <wuzhangjin@gmail.com>

(This v5 revision incorporates with the feedbacks from Ingo.)

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 <wuzhangjin@gmail.com>

diff --git a/arch/mips/kernel/csrc-r4k-hres.c b/arch/mips/kernel/csrc-r4k-hres.c
new file mode 100644
index 0000000..2fe8be7
--- /dev/null
+++ b/arch/mips/kernel/csrc-r4k-hres.c

I don't think this is really good name for this file (one might think that this is another implementation of clocksource instead of some sched_clock() code tied to this particular clocksource), and I don't think we indeed needed to separate that thing into a file of its own, i.e. I'm against Ingo's suggestion in this case.

WBR, Sergei

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