Re: ntdll WRITECOPY dropped from staging

Hi Fabian,

It should be done with userfaultfd. I have a WIP branch at https://gitlab.winehq.org/zhiyi/wine/-/tree/bug-23670-implement-write-copy-with-userfaultfd.
The writecopy part is working. However, the performance impact is a concern. Some games call |VirtualQuery() tens of thousands of times and any slowdown
makes these games stutter. Also, Paul mentioned that we should implement making shared pages private and make it work alongside PAGE_WRITECOPY so that
it's both correct feature wise and performance wise. It needs more work.

As for why not using signals to track page faults for implementing WRITECOPY. There are a few issues with that approach. First, it's too slow. Second, signals
may be blocked.
|
Best Regards,
Zhiyi

On 9/29/24 01:55, Fabian Maurer wrote:
> Hello,
>
> I noticed that the ntdll WRITECOPY changes got mostly dropped from staging in
> commit https://github.com/wine-staging/wine-staging/commit/
> 16dce521242b3f4a52cd2c8799ce6fe464fac83c
>
>> The current state even after multiple iterations, the whole
>> WRITECOPY implemenet needs differently.  Upstream will need to
>> do this.
> As I understand it, the implementation marks WRITECOPY pages as read-only on
> the unix side, handling the access violation and marking it as read-write
> afterwards. (Correct me if I'm wrong)
>
> What is wrong with the underlying concept, how should it be implemented
> properly?
>
> Regards,
> Fabian Maurer
>
>
>
>  
>