the current status of RT_PREEMPT for mips

the current status of RT_PREEMPT for mips

[wuzj]

HI!

I'm planning to port RE_PREEMPT to loongson2f(a mipsel compatible
processor), the "FAQ" web page of RTWiKi(rt.wiki.kernel.org) shows that
"There are systems representing the x86, x86_64, ARM, MIPS, and Power
architectures using the CONFIG_PREEMPT_RT patch.", does it means that
RT_PREEMPT support  MIPS architecture? because i can not find any more
information about it, I tried to use the latest RT_PREEMPT on qemu
0.9.1/mipssim, it can not boot, so I come to get your help, could you give
any current status of RT_PREEMPT for mips? such as:

1. does the latest RT_PREEMPT(for linux 2.6.26.8) support MIPS
architecture? or any older one support it?
2. if Yes, which MIPS processors have been successfully running RT_PREEMPT?

looking forward to your reply, thanks!

Best Regards,
falcon

Re: the current status of RT_PREEMPT for mips

[Frank Rowand]

wuzj@lemote.com wrote:
> HI!
> 
> I'm planning to port RE_PREEMPT to loongson2f(a mipsel compatible
> processor), the "FAQ" web page of RTWiKi(rt.wiki.kernel.org) shows that
> "There are systems representing the x86, x86_64, ARM, MIPS, and Power
> architectures using the CONFIG_PREEMPT_RT patch.", does it means that
> RT_PREEMPT support  MIPS architecture? because i can not find any more
> information about it, I tried to use the latest RT_PREEMPT on qemu
> 0.9.1/mipssim, it can not boot, so I come to get your help, could you give
> any current status of RT_PREEMPT for mips? such as:
> 
> 1. does the latest RT_PREEMPT(for linux 2.6.26.8) support MIPS
> architecture? or any older one support it?
> 2. if Yes, which MIPS processors have been successfully running RT_PREEMPT?
> 
> looking forward to your reply, thanks!
> 
> Best Regards,
> falcon

I do not have information for current versions of the kernel, but last year
I was running 2.6.24-rt1 on a Toshiba tx4937 to do some experiments.

I have a few trivial patches for the latency tracer, but if you use a newer
kernel they are not needed because ftrace replaced the latency tracer
in 2.6.24-rt2.

-Frank Rowand
Sony Corporation of America

Re: the current status of RT_PREEMPT for mips

[wuzj]

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wuzj@xxxxxxxxxx wrote:
>> HI!
>>
>> I'm planning to port RE_PREEMPT to loongson2f(a mipsel compatible
>> processor), the "FAQ" web page of RTWiKi(rt.wiki.kernel.org) shows that
>> "There are systems representing the x86, x86_64, ARM, MIPS, and Power
>> architectures using the CONFIG_PREEMPT_RT patch.", does it means that
>> RT_PREEMPT support MIPS architecture? because i can not find any more
>> information about it, I tried to use the latest RT_PREEMPT on qemu
>> 0.9.1/mipssim, it can not boot, so I come to get your help, could you give
>> any current status of RT_PREEMPT for mips? such as:
>>
>> 1. does the latest RT_PREEMPT(for linux 2.6.26.8) support MIPS
>> architecture? or any older one support it?
>> 2. if Yes, which MIPS processors have been successfully running
RT_PREEMPT?
>>
>> looking forward to your reply, thanks!
>>
>> Best Regards,
>> falcon

> I do not have information for current versions of the kernel, but last year
> I was running 2.6.24-rt1 on a Toshiba tx4937 to do some experiments.

thanks very much, currently, there are two versions of rt-preempt working
on fuloong box(loongson2f based machine), one is linux-2.6.26.8, another
is the latest linux-2.6.29-rc6.

and i have tested them via rt-tests, the result is like this:

0% load:  < 29us
100% load: < 130 us

> I have a few trivial patches for the latency tracer, but if you use a newer
> kernel they are not needed because ftrace replaced the latency tracer
> in 2.6.24-rt2.

now, ftrace have been migrated to mipsel(loongson2f), including the 32bit
and 64bit. but dyn-ftrace not work yet, which should be fixed later.

and about timestamp information in ftrace, the sched_clock(called by
ring_buffer_time_stamp) have not enough precision(only 1000us) on
mips(loongson2f), i have tried to fix it via adding it with the tsc
time(in kernel/trace/ring_buffer.c):

cyc2ns(clock, clock->read() - clock->cycle_last)

which seems works well(achieve 1us). and i have tried to call
getnstimeofday directly, but it will result in deadlock.

> -Frank Rowand
> Sony Corporation of America

the attachments include two files:

patch-2.6.29-rc6-fl-090305  linux patch for loongson2f
patch-2.6.29-rc6-fl-rt-ftrace-mips rt-preempt patch for mipsel(loongson2f)

usage:

1. download the following files

from www.kernel.org:

linux-2.6.28.tar.gz
patch-2.6.29-rc6

from http://www.kernel.org/pub/linux/kernel/projects/rt/:

patch-2.6.29-rc6-rt3

2. decompress linux kernel
3. patch the following patches one by one

patch-2.6.29-rc6
patch-2.6.29-rc6-fl-090305
patch-2.6.29-rc6-rt3
patch-2.6.29-rc6-fl-rt-ftrace-mips

4. configure, compile and use it.

PS: kft(Kernel function tracing) patch for linux-2.6.29-rc6 is also
running on loongson2f now.

[-- Attachment #2: patch-2.6.29-rc6-fl-090305.tar.gz --]
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[-- Attachment #3: patch-2.6.29-rc6-fl-rt-ftrace-mips.tar.gz --]
[-- Type: application/x-gzip, Size: 14877 bytes --]