Re: tb_flush() calls causing long Windows XP boot times

[Programmingkid]

> On Jun 15, 2021, at 9:58 PM, Richard Henderson <richard.henderson@linaro.org> 
> wrote:
> 
> On 6/15/21 6:58 AM, Programmingkid wrote:
>>> Ahh I misread - so those are the addresses of the routines and not where
>>> it's sticking the breakpoint?
>>> 
>>> I notice from a bit of googling that there is a boot debugger. I wonder
>>> if /nodebug in boot.ini stops this behaviour?
>>> 
>>>  
>>> https://docs.microsoft.com/en-us/troubleshoot/windows-server/performance/switch-options-for-boot-files
>>> 
>>> -- 
>>> Alex Bennée
>> Hi Alex,
>> I tried your suggestion of using /nodebug. It did not stop the tb_flush() 
>> function from being called.
> 
> We are not expecting zero calls to tb_flush (it is used for other things, 
> including buffer full), but we are hoping that it reduces the frequency of 
> the calls.

Agreed.

> I'm guessing you didn't immediately see the slowdown vanish, and so there was 
> no change to the frequency of the calls.

Correct.

> FWIW, if you switch to the qemu console, you can see how many flushes have 
> occurred with "info jit".

Thank you very much for this information.

I'm currently learning about the x86's debug registers D0 to D7. There are a 
lot of rules associated with them. So my guess is one or more rules may not be 
implemented in QEMU. I will try to test them out in FreeDOS and compare notes 
with a real x86 CPU.

A possible workaround might be to implement a command line option that allows 
the user to specify how often the tb_flush() call is made. When I eliminated 
the call I could not find any problems with my VM's. I understand if this is 
not possible.