Mel Gorman wrote:
> It has been asserted that the name get_huge_pages() implies the API is
> a close-to-kernel interface for allocating hugepages and nothing else.
> In 2.1-preX, this definition does not fit as it allows fallback to base pages
> for example. This patch enforces the meaning implied by the function name by
> removing the ability of the function to fallback to base pages and redefines
> GHP_DEFAULT to mean "Use the default hugepage size to back the region".
>
> Signed-off-by: Mel Gorman <[EMAIL PROTECTED]>
> ---
> alloc.c | 22 +++++++------------
> hugetlbfs.h | 10 ++------
> man/get_huge_pages.3 | 20 ++++++++++--------
> tests/get_huge_pages.c | 53
> ------------------------------------------------
> 4 files changed, 22 insertions(+), 83 deletions(-)
>
> diff --git a/alloc.c b/alloc.c
> index c118f18..6e026c5 100644
> --- a/alloc.c
> +++ b/alloc.c
> @@ -65,15 +65,13 @@ static void *fallback_base_pages(size_t len, ghp_t flags)
>
> /**
> * get_huge_pages - Allocate an amount of memory backed by huge pages
> - * len: Size of the region to allocate
> + * len: Size of the region to allocate, must be hugepage-aligned
> * flags: Flags specifying the behaviour of the function
> *
> - * This function allocates a region of memory backed by huge pages and
> - * at least hugepage-aligned. This is not a suitable drop-in for malloc()
> - * and is only suitable in the event the length is expected to be
> - * hugepage-aligned. However, a malloc-like library could use this function
> - * to create additional heap similar in principal to what morecore does for
> - * glibc malloc.
> + * This function allocates a region of memory that is backed by huge pages
> + * and hugepage-aligned. This is not a suitable drop-in for malloc() but a
> + * a malloc library could use this function to create a new fixed-size heap
> + * similar in principal to what morecore does for glibc malloc.
> */
> void *get_huge_pages(size_t len, ghp_t flags)
> {
> @@ -93,10 +91,6 @@ void *get_huge_pages(size_t len, ghp_t flags)
> if (buf == MAP_FAILED) {
> close(heap_fd);
>
> - /* Try falling back to base pages if allowed */
> - if (flags & GHP_FALLBACK)
> - return fallback_base_pages(len, flags);
> -
> WARNING("get_huge_pages: New region mapping failed (flags:
> 0x%lX): %s\n",
> flags, strerror(errno));
> return NULL;
> @@ -107,9 +101,9 @@ void *get_huge_pages(size_t len, ghp_t flags)
> munmap(buf, len);
> close(heap_fd);
>
> - /* Try falling back to base pages if allowed */
> - if (flags & GHP_FALLBACK)
> - return fallback_base_pages(len, flags);
> + WARNING("get_huge_pages: Prefaulting failed (flags: 0x%lX):
> %s\n",
> + flags, strerror(errno));
> + return NULL;
> }
>
> /* Close the file so we do not have to track the descriptor */
> diff --git a/hugetlbfs.h b/hugetlbfs.h
> index 0694a0b..0efa02c 100644
> --- a/hugetlbfs.h
> +++ b/hugetlbfs.h
> @@ -40,16 +40,12 @@ int hugetlbfs_unlinked_fd_for_size(long page_size);
> #define PF_LINUX_HUGETLB 0x100000
>
> /*
> - * Direct alloc flags and types
> + * Direct hugepage allocation flags and types
> *
> - * GHP_DEFAULT - Use a combination of flags deemed to be a sensible default
> - * by the current implementation of the library
> - * GHP_FALLBACK - Use the default hugepage size if possible but fallback to
> - * smaller pages if necessary
> + * GHP_DEFAULT - Use the default hugepage size to back the region
> */
> typedef unsigned long ghp_t;
> -#define GHP_FALLBACK (0x01UL)
> -#define GHP_DEFAULT (0)
> +#define GHP_DEFAULT ((ghp_t)0x01UL)
>
> /* Direct alloc functions */
> void *get_huge_pages(size_t len, ghp_t flags);
> diff --git a/man/get_huge_pages.3 b/man/get_huge_pages.3
> index a2173f8..f2a33a4 100644
> --- a/man/get_huge_pages.3
> +++ b/man/get_huge_pages.3
> @@ -16,7 +16,7 @@
> .\" .sp <n> insert n+1 empty lines
> .\" for manpage-specific macros, see man(7)
> .SH NAME
> -get_huge_pages, free_huge_pages \- Allocate and free memory regions backed
> by hugepages
> +get_huge_pages, free_huge_pages \- Allocate and free hugepages
> .SH SYNOPSIS
> .B #include <hugetlbfs.h>
> .br
> @@ -33,19 +33,19 @@ large amounts of address space and suffer a performance
> hit due to TLB
> misses. Wall-clock time or oprofile can be used to determine if there is
> a performance benefit from using hugepages or not.
>
> +The \fBlen\fP parameter must be hugepage-aligned. In the current
> +implementation, only the default hugepage size may be allocated via this
> +function. Use \fBgethugepagesize\fP to discover what the alignment should
> +be.
> +
> The \fBflags\fP argument changes the behaviour
> of the function. Flags may be or'd together.
>
> .TP
> .B GHP_DEFAULT
> -Allocate a region of memory of the requested length backed by
> -hugepages. Return NULL if sufficient pages are not available
>
> -.TP
> -.B GHP_FALLBACK
> -Allocate a region of memory backed by hugepages. If sufficient hugepages
> -are not available, return an MAP_ANONYMOUS region of memory backed by base
> -page-sized pages instead.
> +Allocate a region of memory of the requested length backed by hugepages of
> +the default hugepage size. Return NULL if sufficient pages are not available
>
> .PP
>
> @@ -55,13 +55,15 @@ is used, valid or otherwise, is undefined.
>
> .SH RETURN VALUE
>
> -For \fBget_huge_pages()\fP, return a pointer to the allocated memory. On
> +On success, a pointer is returned for to the allocated memory. On
>
Phrasing seems awkward. Either 'for' or 'to' is not needed.
Jon
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