Messages in this thread | | | Date | Wed, 12 Aug 2009 21:53:25 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: vma_merge issue |
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On Wed, 12 Aug 2009, Hugh Dickins wrote: > > Don't use anonymous memory, have a 1GB sparse file to back this, > and mmap it MAP_SHARED, then you won't get charged for RAM+swap.
A "refinement" to that suggestion is to put the file on tmpfs: you will then get charged for RAM+swap as you use it, but you can use madvise MADV_REMOVE to unmap pages, punching holes in the file, freeing up those charges. A little baroque, but I think it does amount to a way of doing exactly what you wanted in the first place.
(Note: we do insist on PROT_WRITE access at the time of MADV_REMOVE: I've even a feeling it was me who insisted on that.)
Hugh
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