Re: the stuttering regression in 7.0: should I have done something different

On 5/12/26 1:17 AM, Thomas Gleixner wrote:
>> [  249.004209] [<0000000000000000>] 0x0
>> [  249.019116] Dumping ftrace buffer:
>> [  249.025666] ---------------------------------
>> [  249.034534]   <idle>-0         0d.... 1836659us :
>> clockevents_program_event: Successfully programmed 4000000 4000000
>> [  249.055418]   <idle>-0         0d.h.. 1845926us : timer_interrupt:
> So this is the interesting part, but that's starting at 1.836659s
> while the actual problem happens ~120 seconds later and the detection
> takes another 120 seconds.
>
> Assuming that one of the CPUs does not get timer interrupts anymore, the
> trace of that CPU should end around the time the last programming
> happened. So the interesting part is at the end of the output. The
> default buffer size per CPU is 1408k, which holds about 150k entries, so
> we can just shorten the buffers to make this less painful.
>
> Can you add 'trace_buf_size=50k' to the kernel command line, which
> limits the buffer size to about 640 entries. Assuming 115200 Baud this
> should then take about 4 seconds per CPU to dump, which still is a bunch
> on a large machine, but definitely way more workable than the default.

Done.  The complete trace file "s7-2-05122026-dump.tar.gz" can be 
obtained from my GitHub repo:

https://github.com/unixpro1970/Sparc64-Kernel-Debugging-Dumps

> IIRC, SPARC64 S7‑2 has 128 threads total, so the resulting uncompressed
> output should be around 7-8M. That's highly compressable text, so the
> resulting dump.xz should be suitable to be stored in github. If github
> does not allow you, let me know and we work something out.
>
> Thanks,
>
>          tglx
>