On Sun, Oct 30, 2022 at 4:42 AM Alejandro Colomar <alx.manpages@xxxxxxxxx> wrote: > > Hi Zach! > > On 10/22/22 00:32, Zach OKeefe wrote: > > From: Zach O'Keefe <zokeefe@xxxxxxxxxx> > > > > Since Linux 5.4, Transparent Huge Pages now support both file-backed > > memory and shmem memory. Update MADV_HUGEPAGE advice description to > > reflect this. > > > > Additionally, expand the description of requirements for memory to be > > considered eligible for THP: alignment / mapping requirements, VMA > > flags, prctl(2) settings, inode status, etc. > > > > Signed-off-by: Zach O'Keefe <zokeefe@xxxxxxxxxx> > > Patch applied! Thanks. > Since you were interested, I amended it with the following diff: > > > diff --git a/man2/madvise.2 b/man2/madvise.2 > index 64f788ace..48bda703c 100644 > --- a/man2/madvise.2 > +++ b/man2/madvise.2 > @@ -361,9 +361,10 @@ .SS Linux-specific advice values > and file-backed pages. > For all memory types, > memory may only be replaced by huge pages on hugepage-aligned boundaries. > -For file-mapped memory \(em including tmpfs (see > -.BR tmpfs (2)) > -\(em the mapping must also be naturally hugepage-aligned within the file. > +For file-mapped memory > +\(emincluding tmpfs (see > +.BR tmpfs (2))\(em > +the mapping must also be naturally hugepage-aligned within the file. > Additionally, > for file-backed, > non-tmpfs memory, > @@ -382,7 +383,7 @@ .SS Linux-specific advice values > The process must also not have > .B PR_SET_THP_DISABLE > set (see > -.BR prctl (2) ). > +.BR prctl (2)). > .IP > The > .B MADV_HUGEPAGE > > > - The em dashes you used were correct with spaces in both sides; there are those > who use them with spaces in both sides and those who use them with no spaces at > all. And then there are those who put spaces as if they were parentheses > (admittedly this is much less common). I prefer this latter case, since it > makes technical texts more parseable. > > - I used a semantic newline break for the em dashes, since they are similar to a > coma. > > - Removed a spurious space in BR that would have made the formatting weird. > > Cheers, > Thanks for taking the patch, and thanks for taking the time with the explanation! Glad I wasn't *too* far off :) Changes look good to me - thank you! Best, Zach > Alex > > > > --- > > man2/madvise.2 | 38 +++++++++++++++++++++++++++++++++++--- > > 1 file changed, 35 insertions(+), 3 deletions(-) > > > > diff --git a/man2/madvise.2 b/man2/madvise.2 > > index 81cce56af..64f788ace 100644 > > --- a/man2/madvise.2 > > +++ b/man2/madvise.2 > > @@ -320,8 +320,6 @@ Enable Transparent Huge Pages (THP) for pages in the range specified by > > .I addr > > and > > .IR length . > > -Currently, Transparent Huge Pages work only with private anonymous pages (see > > -.BR mmap (2)). > > The kernel will regularly scan the areas marked as huge page candidates > > to replace them with huge pages. > > The kernel will also allocate huge pages directly when the region is > > @@ -354,12 +352,46 @@ an access pattern that the developer knows in advance won't risk > > to increase the memory footprint of the application when transparent > > hugepages are enabled. > > .IP > > +.\" commit 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 > > +Since Linux 5.4, > > +automatic scan of eligible areas and replacement by huge pages works with > > +private anonymous pages (see > > +.BR mmap (2)), > > +shmem pages, > > +and file-backed pages. > > +For all memory types, > > +memory may only be replaced by huge pages on hugepage-aligned boundaries. > > +For file-mapped memory \(em including tmpfs (see > > +.BR tmpfs (2)) > > +\(em the mapping must also be naturally hugepage-aligned within the file. > > +Additionally, > > +for file-backed, > > +non-tmpfs memory, > > +the file must not be open for write and the mapping must be executable. > > +.IP > > +The VMA must not be marked > > +.BR VM_NOHUGEPAGE , > > +.BR VM_HUGETLB , > > +.BR VM_IO , > > +.BR VM_DONTEXPAND , > > +.BR VM_MIXEDMAP , > > +or > > +.BR VM_PFNMAP , > > +nor can it be stack memory or backed by a DAX-enabled device > > +(unless the DAX device is hot-plugged as System RAM). > > +The process must also not have > > +.B PR_SET_THP_DISABLE > > +set (see > > +.BR prctl (2) ). > > +.IP > > The > > .B MADV_HUGEPAGE > > and > > .B MADV_NOHUGEPAGE > > operations are available only if the kernel was configured with > > -.BR CONFIG_TRANSPARENT_HUGEPAGE . > > +.B CONFIG_TRANSPARENT_HUGEPAGE > > +and file/shmem memory is only supported if the kernel was configured with > > +.BR CONFIG_READ_ONLY_THP_FOR_FS . > > .TP > > .BR MADV_NOHUGEPAGE " (since Linux 2.6.38)" > > Ensures that memory in the address range specified by > > -- > <http://www.alejandro-colomar.es/>
