On 26.05.22 20:09, Mike Kravetz wrote: > Clarify that madvise only works on full pages, and remove references > to 'bytes'. > > Update MADV_DONTNEED and MADV_REMOVE sections to remove notes that > HugeTLB mappings are not supported. Indicate the releases when they > were first supported as well as alignment restrictions. > > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > --- BTW, the git repository [1] was last updated 2021-09-02. One of my patches [2] was apparently picked up (reply via mail) but doesn't appear in that repository. Is the project currently dead/unmaintained or am I just staring at the wrong repository? [1] https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git [2] https://lkml.kernel.org/r/20210823120645.8223-1-david@xxxxxxxxxx > v1 -> v2 Added releases when Huge TLB support was added and moved > alignment requirements to corresponding section. (Peter) > > man2/madvise.2 | 31 +++++++++++++++++++++---------- > 1 file changed, 21 insertions(+), 10 deletions(-) > > diff --git a/man2/madvise.2 b/man2/madvise.2 > index f1f384c0c..50686e7e3 100644 > --- a/man2/madvise.2 > +++ b/man2/madvise.2 > @@ -61,9 +61,13 @@ system call is used to give advice or directions to the kernel > about the address range beginning at address > .I addr > and with size > +.IR length . > +.BR madvise () > +only operates on whole pages, therefore > +.I addr > +must be page-aligned. The value of > .I length > -bytes > -In most cases, > +is rounded up to a multiple of page size. In most cases, > the goal of such advice is to improve system or application performance. > .PP > Initially, the system call supported a set of "conventional" > @@ -143,7 +147,7 @@ The resident set size (RSS) of the calling process will be immediately > reduced however. > .IP > .B MADV_DONTNEED > -cannot be applied to locked pages, Huge TLB pages, or > +cannot be applied to locked pages, or > .BR VM_PFNMAP > pages. > (Pages marked with the kernel-internal > @@ -153,6 +157,11 @@ flag are special memory areas that are not managed > by the virtual memory subsystem. > Such pages are typically created by device drivers that > map the pages into user space.) > +.IP > +Support for Huge TLB pages was added in Linux v5.18. Addresses within a > +mapping backed by Huge TLB pages must be aligned to the underlying Huge TLB > +page size, and the range length is rounded up to a multiple of the underlying > +Huge TLB page size. > .\" > .\" ====================================================================== > .\" > @@ -170,24 +179,24 @@ Note that some of these operations change the semantics of memory accesses. > .\" commit f6b3ec238d12c8cc6cc71490c6e3127988460349 > Free up a given range of pages > and its associated backing store. > -This is equivalent to punching a hole in the corresponding byte > +This is equivalent to punching a hole in the corresponding > range of the backing store (see > .BR fallocate (2)). > Subsequent accesses in the specified address range will see > -bytes containing zero. > +pages containing zero. > .\" Databases want to use this feature to drop a section of their > .\" bufferpool (shared memory segments) - without writing back to > .\" disk/swap space. This feature is also useful for supporting > .\" hot-plug memory on UML. > .IP > The specified address range must be mapped shared and writable. > -This flag cannot be applied to locked pages, Huge TLB pages, or > +This flag cannot be applied to locked pages, or > .BR VM_PFNMAP > pages. > .IP > In the initial implementation, only > .BR tmpfs (5) > -was supported > +supported > .BR MADV_REMOVE ; > but since Linux 3.5, > .\" commit 3f31d07571eeea18a7d34db9af21d2285b807a17 > @@ -196,10 +205,12 @@ any filesystem which supports the > .BR FALLOC_FL_PUNCH_HOLE > mode also supports > .BR MADV_REMOVE . > -Hugetlbfs fails with the error > -.BR EINVAL > -and other filesystems fail with the error > +Filesystems which do not support > +.BR MADV_REMOVE > +fail with the error > .BR EOPNOTSUPP . > +.IP > +Support for Huge TLB filesystem was added in Linux v4.3. > .TP > .BR MADV_DONTFORK " (since Linux 2.6.16)" > .\" commit f822566165dd46ff5de9bf895cfa6c51f53bb0c4 -- Thanks, David / dhildenb
