On 08/23/2010 11:55 AM, David Hilton wrote:
On Mon, Aug 23, 2010 at 11:51 AM, Michael Torrie <[email protected] <mailto:[email protected]>> wrote:On 08/23/2010 11:49 AM, AJ ONeal wrote: > What I mean is will the memory be contiguous in fashion when it is resident. Good question. Not sure. Unlike hard drives where fragmentation hurts you, does it hurt you in memory? Every page access has to go through the VM redirector.Exactly - it makes no difference. The memory subsystem will be taking chunks from ram and pulling them up through the cache heirarchy anyway - nothing uses the ram for operations, and there would be no performance penalty for having fragmented ram.
It can still hurt you because of cache misses. Physical memory fragmentation possibly means more fetches from memory, and depending on how much physical memory is fetched at a time, and cached, you may end up thrashing between cache and memory.
I would *never* optimize my software for this situation until I had proven that it is indeed a performance problem. I have heard of web applications that have needed to optimize for this case, however.
--Dave
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