linux-kernel - Re: "RT_PREEMPT for loongson" is updated to patch-2.6.29.1-rt8

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Message-Id: <1240211926.8884.27.camel@falcon>
Date:	Mon, 20 Apr 2009 15:18:46 +0800
From:	Wu Zhangjin <wuzhangjin@...il.com>
To:	Zhang Le <r0bertz@...too.org>
Cc:	linux-kernel@...r.kernel.org, Nicholas Mc Guire <hofrat@...r.at>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>, zhangfx@...ote.com,
	loongson-dev@...glegroups.com, yanh@...ote.com,
	Ralf Baechle <ralf@...ux-mips.org>, linux-mips@...ux-mips.org,
	linux-rt-users@...r.kernel.org
Subject: Re: "RT_PREEMPT for loongson" is updated to patch-2.6.29.1-rt8

On Mon, 2009-04-20 at 13:04 +0800, Zhang Le wrote:
> Hi, Zhangjin,
> 
> Ralf told me he has a ftrace implementation too.
> 
> 11:47 < Ralf> r0bertz: ftrace looks nice but not yet mergable yet.
> 11:47 < Ralf> r0bertz: I also have my own ftrace implementation which in some
> parts is better, in some is worse. 
> 11:47 < Ralf> r0bertz: So this is going to be quite a job.  
> 
> So I think you can talk to Ralf about how to get this merged, :)
> 

to Zhangle, 

thx very much for your info :-) 

hope Ralf can reply this E-mail and pull the source code from my git
tree:

git://dev.lemote.com/rt4ls.git

to Ralf, 

I have divided ftrace to several commits in the above git tree, hope you
can check it, thx :-) 

in addition to the static/dynamic/graph function tracer & system call
tracer implementation, a mips specific ring_buffer_time_stamp
(kernel/trace/ring_buffer.c) is also implemented to get 1us precision
time, this is very important to make ftrace available in mips,
otherwise, we can only get 1ms precision time for the original
ring_buffer_time_stamp is based on sched_clock(jiffies based). 

perhaps we can implement a more precise sched_clock directly, just as
x86 does(native_sched_clock, tsc based), but in mips, there is only a
32bit timer count which will quickly overflow, so it will need an extra
overflow protection, which may influence the other parts of the kernel.

best regards,
Wu Zhangjin

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