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Optimal string copy performance



 
 
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  #1  
Old March 18th 10, 07:01 AM posted to comp.os.os2.programmer.misc,comp.arch,comp.programming,comp.sys.ibm.pc.hardware.chips
Jonathan de Boyne Pollard
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Posts: 62
Default Optimal string copy performance



I need to copy some RAM memory area to the screen buffer with as good
a performance as possible.

The prerequisites/restrictions a

1.) it has to work under OS/2 - that is with 32-bit legacy - no 64-bit
instructions

2.) if possible it should support INTEL and AMD CPUs but I might think
about processor specific implementations

3.) it should give preference to low irq latency - that is, if a lot
of IRQs need to be serviced, copy performance (and therefore video
refresh performance) can be sacrified against low irq latency/quick
irq response

4.) the solution should outperform the "rep movsd" instruction

Is your VRAM write-back or write-through? Is it write-combining? All
of these things will affect whether your choice of data manipulation
instructions is even significant. (-:

  #2  
Old March 18th 10, 08:52 AM posted to comp.os.os2.programmer.misc,comp.arch,comp.programming,comp.sys.ibm.pc.hardware.chips
Terje Mathisen[_3_]
external usenet poster
 
Posts: 23
Default Optimal string copy performance

Jonathan de Boyne Pollard wrote:


I need to copy some RAM memory area to the screen buffer with as good
a performance as possible.

The prerequisites/restrictions a

[snip]
4.) the solution should outperform the "rep movsd" instruction

Is your VRAM write-back or write-through? Is it write-combining? All of
these things will affect whether your choice of data manipulation
instructions is even significant. (-:


Even more interesting is the issue of why he thinks the code
could/should affect hw interrupt response times!

This pretty much means that he's thinking about running this copy code
in kernel mode, with interrupts disabled, something that stopped making
sense around the time of the original EGA/VGA adapters!

Terje

PS. Why the original cross-poster thinks this is even marginally
relevant to comp.arch beats me.:-(

--
- Terje.Mathisen at tmsw.no
"almost all programming can be viewed as an exercise in caching"
 




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