RE: XP2 slowdowns?

LUA does not use a JIT, so that's not what it is. Bytecodes
are not native x86 instructions; they're just data that the
LUA interpreter loop reads and (basically) does a big switch
on.

Further, the DEP is implemented using hardware traps, the
same way as non-writable (or non-mapped) memory is. Thus, the
OS doesn't need to spend extra time on it; it flips a bit in
the page table, and if you ever try to execute on that page,
the CPU will get an interrupt, similar to a segv if you write
to un-mapped memory.

Sadly, only the very newest, most expensive CPUs support the
executable permission bit on the x86 architecture, so most
CPUs don't have the ability to trap data execution. Thus,
Microsoft added something they call Software-enforced data
execution prevention. However, that code only gets run when
an exception is triggered (SegV, etc), AND if the binary that
triggers the exception is re-compiled to support the checks;
all this does is making sure that the exception handler is an
address that's a bona fide function export from your binary.

If the idle thread is busy, it means that your process is
blocked on some blocking primitive (synchronization somewhere)
held by some other process. Thus, if there's a high idle CPU
utilization, try removing specific calls to Windows APIs until
the problem goes away; then you know what changed.

Cheers,

			/ h+


-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of
Brett Bibby
Sent: Monday, September 06, 2004 4:12 AM
To: [email protected]
Subject: Re: [GD-Windows] XP2 slowdowns?


I came across this:
http://www.microsoft.com/technet/prodtechnol/winxppro/maintain/sp2mempr.mspx

Since our game is script driven (Lua) I'm wondering if that other 50% of
Windows CPU time is being used to check the execute permissions of the
software Data Execution Prevention (DEP) permission? It specifically
cautions JIT code may be broken. We don't mark the page block as executable
and load the Lua bytecodes into RAM allocated form the heap.

Has anybody else using scripts noticed any performance penalties? Can
anybody see any reason why the DEP could be the cause?

Thanks,
Brett

----- Original Message -----
From: "mike wuetherick" <[email protected]>
To: <[email protected]>
Sent: Monday, September 06, 2004 12:06 PM
Subject: Re: [GD-Windows] XP2 slowdowns?


> i've read other reports online about similar slowdowns related to sp2, but
> nothing pointing to a specific issue.
>
> i think it's just windows twiddling with the swap file and other crap -
> there needs to be a way to tell windows 'the computer is busy now, dont do
> anything until further notice'...i've seen situations where windows
> decides to random start defragging mid-game that type of thing.
>
> just idiotic behavior from such a so-called 'smart os' but i digress.
>
> unfortunately the only way to probably fix this is to shut down services
> that are running maintenance or whatever, which isn't exactly an
> 'end-user' fix...
>
> we updated one machine to sp2 and it was an all-day nightmare, haven't
> even considered putting it onto anything else yet.
>
> the college i teach at isn't going near it for a long time i know as well.
>
> mike w
> www.realityfactory.ca
>
> Brett Bibby wrote:
>
>> Hello,
>> We upgraded some of our development machines using XP to SP2 and the
>> upgraded machines _sometimes_ run our game slower now. When I watch the
>> processes while the game runs, the game frequently drops to 20-50% of
>> CPU, with the windows idle occupying the other 50%, so our game is
>> sometimes not consuming as much of the CPU as desired. Has anybody else
>> noticed any speed problems with their games?
>> Thanks,
>> Brett
>>
>
>
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