On 05/08/2014 10:38 PM, Andy Lutomirski wrote: > On Thu, May 8, 2014 at 6:29 AM, Michael Kerrisk (man-pages) > <mtk.manpages@xxxxxxxxx> wrote: >> Hi Christoph, >> >> On Thu, May 8, 2014 at 2:50 PM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: >>> On Thu, May 08, 2014 at 11:45:05AM +0200, Michael Kerrisk (man-pages) wrote: >>>> I've applied the above. I then tweaked it a little. Is the following >>>> okay: >>>> >>>> [[ >>>> Since Linux 2.6.23, >>>> .\" commit 3ee6dafc677a68e461a7ddafc94a580ebab80735 >>>> .BR remap_file_pages () >>>> has no performance advantage over >>>> .BR mmap (2) >>>> when used on real files: >>>> on real files it creates a separate VMA for each range. >>>> It does, however, continue to provide a performance advantage >>>> for files on memory-based filesystems. >>>> ]] >>> >>> I think "real file" is a very bad term. What is more real about one >>> file vs another? Is NFS less real than XFS, is tmpfs more real than >>> ramfs? >>> >>> I'd reword this more like this: >>> >>> Since Linux 2.6.23, remap_file_pages only creates non-linear mappings >>> on in-memory file systems like tmpfs, hugetlbfs or ramfs. File systems >>> with a backing store provide a less efficient emulation. >> >> Yes, sounds better to me. Any tweaks you want to add to that, Andy? >> >>> I think the whole man page for remap_file_pages is a litt confusing I >>> have to say, the concept of a VMA is purely kernel internal and doesn't >>> really have a meaning for applications and thus shouldn't appear in a >>> man page. >> >> I agree it could be better. Do you have a suggested text? >> >>> While we're at it: It seems like we should get rid of the remap_pages >>> vma operation - it's set by lots of filesystems that can never have >>> it invoked, and always is set to generic_file_remap_pages anyway. > > Something along the lines of "on filesystems with a backing store, > remap_file_pages is not much more efficient than using mmap(2) to > adjust which parts of the file are mapped to which addresses" might > get the idea across. So, now I have: [[ Since Linux 2.6.23, .\" commit 3ee6dafc677a68e461a7ddafc94a580ebab80735 .BR remap_file_pages () creates non-linear mappings only on on in-memory file systems such as tmpfs, hugetlbfs or ramfs. On filesystems with a backing store, .BR remap_file_pages () is not much more efficient than using .BR mmap (2) to adjust which parts of the file are mapped to which addresses. ]] Okay? Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
