Virtual allocation granularity and page size

c windows winapi win64
fbonnet picture fbonnet · Jan 13, 2009 · Viewed 7.1k times · Source

What are the typical values of the virtual allocation granularity and page size on Win64 platforms? That'd be SYSTEM_INFO's dwAllocationGranularity and dwPageSize.

On Win32 systems these would be 64k and 4k.

I need to know because I've designed a custom allocator based on VirtualAlloc for a Win32 application and wonder if my design choices are still valid on Win64. I have no access to a Win64 system.

Thanks in advance!

Answer

Hans Passant picture Hans Passant · Jan 13, 2009

It is still the same, 64k and 4k on Vista x64. Not so sure if that isn't going to change some day, the small page size is putting serious pressure on the TLB cache, degrading perf considerably for programs that allocate multi-gigabyte chunks. I've also seen several problem reports about not being able to allocate large pages anymore at some inscrutable point during program execution. But that's just crystal-ball staring for now.

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