SIMD Instruction supported in UEFI?

SIMD Instruction supported in UEFI?

[Amit kumar]

Hi ;
I have written a UEFI app in ASM which runs XOR on a block of data using SIMD instructions ("PXOR") in UEFI environment.
It takes around 2 Seconds to run this code, but when i use normal C XOR operator ("^") it takes 1 Seconds.
Is there something wrong ? I mean SIMD instructions must be giving me better performance(my expectation);

But when i do same experiment in Windows environment SIMD code ( _mm_xor_si128 ) gives me 9 times better performance than normal XOR instruction.       

 Have i missed something?.

Regards
Amit Kumar

Re: SIMD Instruction supported in UEFI?

[Ken Taylor]

Hi Amit,

Maybe in UEFI the code in question crosses a cache line boundary when executed in UEFI, with the loop or part of the instruction itself on one side of the boundary and the rest on the other?  At what point are you trying to execute this code, is it still from the UEFI shell or have you moved it into a driver that runs earlier?

You might try changing the linker flags to force 4k code alignment on your test binary.

Regards,
-Ken.

-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Amit kumar
Sent: Wednesday, March 08, 2017 7:10 AM
To: edk2-devel@lists.01.org
Subject: [edk2] SIMD Instruction supported in UEFI?


Hi ;
I have written a UEFI app in ASM which runs XOR on a block of data using SIMD instructions ("PXOR") in UEFI environment.
It takes around 2 Seconds to run this code, but when i use normal C XOR operator ("^") it takes 1 Seconds.
Is there something wrong ? I mean SIMD instructions must be giving me better performance(my expectation);

But when i do same experiment in Windows environment SIMD code ( _mm_xor_si128 ) gives me 9 times better performance than normal XOR instruction.       

 Have i missed something?.

Regards
Amit Kumar
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Re: SIMD Instruction supported in UEFI?

[Amit kumar]

>From UEFI shell




From: Ken Taylor <Ken_Taylor@phoenix.com>
Sent: Thursday, March 9, 2017 4:51 AM
To: Amit kumar; edk2-devel@lists.01.org
Subject: RE: [edk2] SIMD Instruction supported in UEFI?
    
Hi Amit,

Maybe in UEFI the code in question crosses a cache line boundary when executed in UEFI, with the loop or part of the instruction itself on one side of the boundary and the rest on the other?  At what point are you trying to execute this code, is it still from  the UEFI shell or have you moved it into a driver that runs earlier?

You might try changing the linker flags to force 4k code alignment on your test binary.

Regards,
-Ken.

-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Amit kumar
Sent: Wednesday, March 08, 2017 7:10 AM
To: edk2-devel@lists.01.org
Subject: [edk2] SIMD Instruction supported in UEFI?


Hi ;
I have written a UEFI app in ASM which runs XOR on a block of data using SIMD instructions ("PXOR") in UEFI environment.
It takes around 2 Seconds to run this code, but when i use normal C XOR operator ("^") it takes 1 Seconds.
Is there something wrong ? I mean SIMD instructions must be giving me better performance(my expectation);

But when i do same experiment in Windows environment SIMD code ( _mm_xor_si128 ) gives me 9 times better performance than normal XOR instruction.      

 Have i missed something?.

Regards
Amit Kumar
_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel