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0 pointsnkurz11y ago0 comments

Perhaps you know: on Linux, how do mmap() and brk() differ as far as page initialization? Does brk() conceptually include the effects of MAP_POPULATE? Do both of them cause virtual to physical memory mapping at the time of the call?

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duaneb11y ago

I'm not sure as to the specifics, because brk is a strict subset of mmap; however, I would be surprised if it doesn't use the full VM substructure to allocate the mapping immediately.

I would amend my statement before to say that, if you're looking into memory allocation, conceptually, mmap is where everything happens these days. brk is kept for backwards compatibility.

lgeek11y ago

On the systems I've seen, brk makes a lazy allocation, i.e. it doesn't allocate physical memory until you write to a page.

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