What is the exact difference between MEM_RESERVE and MEM_COMMIT states?
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Published on 2010-03-30T15:07:56Z
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2010/03/30
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As I understand it MEM_RESERVE is actually 'free' memory, ie available to be used by my process, but just hasn't been allocated yet? Or it was previously allocated, but had since been freed?
Specifically, see in my !address output below how I am nearly out of virtual address space (99900 KB free, 2307872 as MEM_PRIVATE. But the states shows that 44.75% of that is actually MEM_RESERVE. Does that mean it is actually free, in my process...but maybe fragmented?
0:000> !address -summary
--------- PEB a8bd8000 not found ----
-------------------- Usage SUMMARY --------------------------
TotSize ( KB) Pct(Tots) Pct(Busy) Usage
259af000 ( 616124) : 22.29% 23.12% : RegionUsageIsVAD
618f000 ( 99900) : 03.61% 00.00% : RegionUsageFree
13e22000 ( 325768) : 11.78% 12.22% : RegionUsageImage
42c04000 ( 1093648) : 39.56% 41.04% : RegionUsageStack
42d000 ( 4276) : 00.15% 00.16% : RegionUsageTeb
2625d000 ( 625012) : 22.61% 23.45% : RegionUsageHeap
0 ( 0) : 00.00% 00.00% : RegionUsagePageHeap
0 ( 0) : 00.00% 00.00% : RegionUsagePeb
1000 ( 4) : 00.00% 00.00% : RegionUsageProcessParametrs
1000 ( 4) : 00.00% 00.00% : RegionUsageEnvironmentBlock
Tot: a8bf0000 (2764736 KB) Busy: a2a61000 (2664836 KB)
-------------------- Type SUMMARY --------------------------
TotSize ( KB) Pct(Tots) Usage
618f000 ( 99900) : 03.61% : <free>
13e22000 ( 325768) : 11.78% : MEM_IMAGE
1e77000 ( 31196) : 01.13% : MEM_MAPPED
8cdc8000 ( 2307872) : 83.48% : MEM_PRIVATE
-------------------- State SUMMARY --------------------------
TotSize ( KB) Pct(Tots) Usage
57235000 ( 1427668) : 51.64% : MEM_COMMIT
618f000 ( 99900) : 03.61% : MEM_FREE
4b82c000 ( 1237168) : 44.75% : MEM_RESERVE
Largest free region: Base 7e4a1000 - Size 000ff000 (1020 KB)
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