[RFC] linux: add definitions for hugetlb page size encodings
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Commit Message
A desired hugetlb page size can be encoded in the flags parameter of
system calls such as mmap() and shmget(). The Linux UAPI headers have
included explicit definitions for these encodings since v4.14.
This patch adds these definitions that are used along with MAP_HUGETLB
and SHM_HUGETLB flags as specified in the corresponding man pages. This
relieves programs from having to duplicate and/or compute the encodings
manually.
Signed-off-by: Carlos Llamas <cmllamas@google.com>
---
sysdeps/unix/sysv/linux/bits/mman-linux.h | 21 ++++++++++++++++++++-
sysdeps/unix/sysv/linux/bits/shm.h | 22 ++++++++++++++++++++++
2 files changed, 42 insertions(+), 1 deletion(-)
Comments
* Carlos Llamas:
> A desired hugetlb page size can be encoded in the flags parameter of
> system calls such as mmap() and shmget(). The Linux UAPI headers have
> included explicit definitions for these encodings since v4.14.
>
> This patch adds these definitions that are used along with MAP_HUGETLB
> and SHM_HUGETLB flags as specified in the corresponding man pages. This
> relieves programs from having to duplicate and/or compute the encodings
> manually.
I think doing this is reasonable. Please remove the MAP_UGE_* filter in
sysdeps/unix/sysv/linux/tst-mman-consts.py, too.
> +/* When MAP_HUGETLB is set, bits [26:31] encode the log2 of the huge page size.
> + The following definitions are associated with this huge page size encoding.
> + It is responsibility of the application to know which sizes are supported on
> + the running system. See mmap(2) man page for details. */
GNU style requires and extra space here: "details. */”
Also applies to <bits/shm.h>.
Thanks,
Florian
On Mon, Jun 17, 2024 at 09:06:40AM +0200, Florian Weimer wrote:
> * Carlos Llamas:
>
> > A desired hugetlb page size can be encoded in the flags parameter of
> > system calls such as mmap() and shmget(). The Linux UAPI headers have
> > included explicit definitions for these encodings since v4.14.
> >
> > This patch adds these definitions that are used along with MAP_HUGETLB
> > and SHM_HUGETLB flags as specified in the corresponding man pages. This
> > relieves programs from having to duplicate and/or compute the encodings
> > manually.
>
> I think doing this is reasonable. Please remove the MAP_UGE_* filter in
> sysdeps/unix/sysv/linux/tst-mman-consts.py, too.
Added to v2.
> > +/* When MAP_HUGETLB is set, bits [26:31] encode the log2 of the huge page size.
> > + The following definitions are associated with this huge page size encoding.
> > + It is responsibility of the application to know which sizes are supported on
> > + the running system. See mmap(2) man page for details. */
>
> GNU style requires and extra space here: "details. */”
>
> Also applies to <bits/shm.h>.
Also added to v2.
Thanks,
Carlos Llamas
@@ -54,10 +54,29 @@
# define MAP_ANONYMOUS 0x20 /* Don't use a file. */
#endif
#define MAP_ANON MAP_ANONYMOUS
-/* When MAP_HUGETLB is set bits [26:31] encode the log2 of the huge page size. */
+
+/* When MAP_HUGETLB is set, bits [26:31] encode the log2 of the huge page size.
+ The following definitions are associated with this huge page size encoding.
+ It is responsibility of the application to know which sizes are supported on
+ the running system. See mmap(2) man page for details. */
+
#define MAP_HUGE_SHIFT 26
#define MAP_HUGE_MASK 0x3f
+#define MAP_HUGE_16KB (14 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_64KB (16 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_512KB (19 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_1MB (20 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_2MB (21 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_8MB (23 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_16MB (24 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_32MB (25 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_256MB (28 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_512MB (29 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_1GB (30 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_2GB (31 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_16GB (34U << MAP_HUGE_SHIFT)
+
/* Flags to `msync'. */
#define MS_ASYNC 1 /* Sync memory asynchronously. */
#define MS_SYNC 4 /* Synchronous memory sync. */
@@ -58,6 +58,28 @@ typedef __syscall_ulong_t shmatt_t;
# define SHM_HUGETLB 04000 /* segment is mapped via hugetlb */
# define SHM_NORESERVE 010000 /* don't check for reservations */
+/* When SHM_HUGETLB is set, bits [26:31] encode the log2 of the huge page size.
+ The following definitions are associated with this huge page size encoding.
+ It is responsibility of the application to know which sizes are supported on
+ the running system. See shmget(2) man page for details. */
+
+#define SHM_HUGE_SHIFT 26
+#define SHM_HUGE_MASK 0x3f
+
+#define SHM_HUGE_16KB (14 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_64KB (16 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_512KB (19 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_1MB (20 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_2MB (21 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_8MB (23 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_16MB (24 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_32MB (25 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_256MB (28 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_512MB (29 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_1GB (30 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_2GB (31 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_16GB (34U << SHM_HUGE_SHIFT)
+
struct shminfo
{
__syscall_ulong_t shmmax;