Messages in this thread | | | Date | Tue, 2 Jul 2013 14:06:56 +0800 | From | Zheng Liu <> | Subject | Re: [RFC][PATCH] mm: madvise: MADV_POPULATE for quick pre-faulting |
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On Mon, Jul 01, 2013 at 09:43:29PM -0700, Dave Hansen wrote: > On 07/01/2013 07:37 PM, Zheng Liu wrote: > > FWIW, it would be great if we can let MAP_POPULATE flag support shared > > mappings because in our product system there has a lot of applications > > that uses mmap(2) and then pre-faults this mapping. Currently these > > applications need to pre-fault the mapping manually. > > Are you sure it doesn't? From a cursory look at the code, it looked to > me like it would populate anonymous and file-backed, but I didn't > double-check experimentally.
Thanks for pointing it out. I write a program to test this issue, and it seems to me that it can populate a shared mapping. But in manpage it describes as below:
MAP_POPULATE (since Linux 2.5.46) Populate (prefault) page tables for a mapping. For a file mapping, this causes read-ahead on the file. Later accesses to the mapping will not be blocked by page faults. MAP_POPULATE is only supported for private mappings since Linux 2.6.23.
This page is part of release 3.24 of the Linux man-pages project. I am not sure whether it has been updated or not.
Regards, - Zheng
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