[PATCH v2 1/5] winevulkan: Support prefixing function parameters.

[Paul Gofman]

On 12/10/21 17:36, Rémi Bernon wrote:
>
> Well as far as I could see, in all the measurements I've made for a 
> long while xsavec64 / xrstor64 were the highest hitters, and something 
> like 10% to 30% CPU time spent on these two instructions.
>
> I don't know if that should be part of the "optimized vast majority of 
> cases", but it's the same with Proton or with current upstream Wine. 
> In any case it's way worse and nowhere near the overhead we had a year 
> ago with SSE XMM register spilling from the ABI transitions generated 
> by the compiler.

It is strange. Unlike the current Proton, xrstor64 should not appear at 
all with upstream Wine (unless the app is setting the context for 
threads constantly). Are you sure that is the case with upstream? In 
that case maybe there is some genuine bug or easy optimization 
opportunity involved.

Then, for xsavec64, it is doing saves in one instruction which otherwise 
split in many with compiler generated registers saves. Can it be it 
affects its place in perf top? Overall I don't think perf can show 
anything meaningful on such a fine measurement level due to sampling 
measurements specifics and CPU instruction flow specifics. A good and 
simple way would be to measure the time over a large amount of calls 
with rdtsc with and without xsavec, in the real game by instrumenting 
the syscall dispatcher with that measurement (fwiw I have such an 
instrumentation for relay stubs locally but not for syscall dispatcher atm).