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PO
 

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    <p>In my understanding of the page table, you have chunks for e.g. 1024 pages, with one word per page each. In any case, it's the number of pages, not allocations, that cost. Hwoever, there might be other mechanisms that cost "extra" per allocation (I just don't know).</p> <p>Still: using VirtualFree you can selectively <strong>decommit</strong> individual pages or page ranges. For a decommitted page, the virtual address range (within your process) is still reserved, but no physical memory (RAM or swap file) is assigned to it. You can later use VirtualAlloc to commit these pages again. </p> <p>So unless you need to free up address space for other allocators within your process, you can use this mechanism to selectively request and return memory to the OS.</p> <p><strong>[edit]</strong> </p> <p><strong>Measuring</strong><br> For measuring, I though of comparing the performance of both algorithms under one or more typical loads (artificial/random allocation pattern, an allocation-heavy "real world" application, etc.). Advantage: you get the "whole story" - Kernel resources, page fragmentation, application performance etc. Disadvantage: you have to implement both algorithms, you don't know the reason, and you probably need very special cases for a measureable difference that sticks out from the noise.</p> <p><strong>Address space fragmentation warning</strong> - be careful with your return algorithm. When returning individual pages to the process in an "whoever is free" fashion, you might end up with an fragmented address space that has 80% of free memory but no 100K of it consecutive.</p>
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    1. POMemory (and other resources) used by individual VirtualAlloc allocation
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    1. COThanks, but it is the address space freeing I am concerned about. De-committing is therefore not enough for me.
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    2. COWell... you could set up a test. let us know what comes of it.
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    3. COBut what to measure and how? How can I measure consumption of kernel internal resources?
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