On Thu, 26 Mar 2015, David Rientjes wrote: > munmap(2) of hugetlb memory requires a length that is hugepage aligned, > otherwise it may fail. Add this to the documentation. > > This also cleans up the documentation and separates it into logical > units: one part refers to MAP_HUGETLB and another part refers to > requirements for shared memory segments. > > Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx> > --- If this is the route we are going to take, this behavoir needs to be called out prominently in the mmap/munmap man page. > Documentation/vm/hugetlbpage.txt | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt > --- a/Documentation/vm/hugetlbpage.txt > +++ b/Documentation/vm/hugetlbpage.txt > @@ -289,15 +289,20 @@ file systems, write system calls are not. > Regular chown, chgrp, and chmod commands (with right permissions) could be > used to change the file attributes on hugetlbfs. > > -Also, it is important to note that no such mount command is required if the > +Also, it is important to note that no such mount command is required if > applications are going to use only shmat/shmget system calls or mmap with > -MAP_HUGETLB. Users who wish to use hugetlb page via shared memory segment > -should be a member of a supplementary group and system admin needs to > -configure that gid into /proc/sys/vm/hugetlb_shm_group. It is possible for > -same or different applications to use any combination of mmaps and shm* > -calls, though the mount of filesystem will be required for using mmap calls > -without MAP_HUGETLB. For an example of how to use mmap with MAP_HUGETLB see > -map_hugetlb.c. > +MAP_HUGETLB. For an example of how to use mmap with MAP_HUGETLB see map_hugetlb > +below. > + > +Users who wish to use hugetlb memory via shared memory segment should be a > +member of a supplementary group and system admin needs to configure that gid > +into /proc/sys/vm/hugetlb_shm_group. It is possible for same or different > +applications to use any combination of mmaps and shm* calls, though the mount of > +filesystem will be required for using mmap calls without MAP_HUGETLB. > + > +When using munmap(2) to unmap hugetlb memory, the length specified must be > +hugepage aligned, otherwise it will fail with errno set to EINVAL. > + > > Examples > ======== > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
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