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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