Re: [PATCH 1/2] accel/tcg/plugin: export host insn size

["Wu, Fei" <fei2.wu@intel.com>]

On 4/11/2023 3:27 PM, Alex Bennée wrote:
> 
> "Wu, Fei" <fei2.wu@intel.com> writes:
> 
>> On 4/10/2023 6:36 PM, Alex Bennée wrote:
>>>
>>> Richard Henderson <richard.henderson@linaro.org> writes:
>>>
>>>> On 4/6/23 00:46, Alex Bennée wrote:
>>>>> If your aim is to examine JIT efficiency what is wrong with the current
>>>>> "info jit" that you can access via the HMP? Also I'm wondering if its
>>>>> time to remove the #ifdefs from CONFIG_PROFILER because I doubt the
>>>>> extra data it collects is that expensive.
>>>>> Richard, what do you think?
>>>>
>>>> What is it that you want from CONFIG_PROFILER that you can't get from perf?
>>>> I've been tempted to remove CONFIG_PROFILER entirely.
>>>
>>> I think perf is pretty good at getting the hot paths in the translator
>>> and pretty much all of the timer related stuff in CONFIG_PROFILER could
>>> be dropped. However some of the additional information about TCG ops
>>> usage and distribution is useful. That said last time I had a tilt at
>>> this on the back of a GSoC project:
>>>
>>>   Subject: [PATCH  v9 00/13] TCG code quality tracking and perf integration
>>>   Date: Mon,  7 Oct 2019 16:28:26 +0100
>>>   Message-Id: <20191007152839.30804-1-alex.bennee@linaro.org>
>>>
>>> The series ended up moving all the useful bits of CONFIG_PROFILER into
>>> tb stats which was dynamically controlled on a per TB basis. Now that
>>> the perf integration stuff was merged maybe there is a simpler series to
>>> be picked out of the remains?
>>>
>>> Fei Wu,
>>>
>>> Have you looked at the above series? Is that gathering the sort of
>>> things you need? Is this all in service of examining the translation
>>> quality of hot code?
>>>
>> Yes, it does have what I want, I suppose this wiki is for the series:
>>     https://wiki.qemu.org/Features/TCGCodeQuality
> 
> Yes.
> 
>>
>> btw, the archive seems broken and cannot show the whole series:
>>     https://www.mail-archive.com/qemu-devel@nongnu.org/msg650258.html
> 
> I have a v10 branch here:
> 
>   https://github.com/stsquad/qemu/tree/tcg/tbstats-and-perf-v10
> 
> I think the top two patches can be dropped on a re-base as the JIT/perf
> integration is already merged. It might be a tricky re-base though.
> Depends on how much churn there has been in the tree since.
> 
I have rebased the patches to upstream here:
    https://github.com/atwufei/qemu/tree/tbstats

I try to keep the patches as possible as they are, but there are lots of
changes since then, so changes are inevitable, e.g. CF_NOCACHE has been
removed from upstream, I just removed its usage in the corresponding
patch, which might not be preferred.

I did some basic tests and they worked (the output of info goes to qemu
console, instead of telnet terminal), including:
    * tb_stats start
    * info tb-list
    * info tb 10

Alex, would you please take a look?

Thanks,
Fei.