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Re: [Qemu-devel] [PATCH] mmap-alloc: tweak a comment on ppc64
From: |
Greg Kurz |
Subject: |
Re: [Qemu-devel] [PATCH] mmap-alloc: tweak a comment on ppc64 |
Date: |
Thu, 3 Dec 2015 10:50:23 +0100 |
On Thu, 3 Dec 2015 10:38:10 +0200
"Michael S. Tsirkin" <address@hidden> wrote:
> The comment I put in mmap-alloc to document the ppc64 rules
> refers to the previous revision of the patch:
> we don't look at memory alignment anymore, we check
> the fs from which the fd is mapped, instead.
>
> It's also not clear what does "in this case" refer
> to, rearrange text to make it clearer.
>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
This is better indeed. Thanks !
Reviewed-by: Greg Kurz <address@hidden>
> util/mmap-alloc.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
> index 54793a5..5cd7f71 100644
> --- a/util/mmap-alloc.c
> +++ b/util/mmap-alloc.c
> @@ -50,10 +50,11 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align,
> bool shared)
> #if defined(__powerpc64__) && defined(__linux__)
> /* On ppc64 mappings in the same segment (aka slice) must share the same
> * page size. Since we will be re-allocating part of this segment
> - * from the supplied fd, we should make sure to use the same page size,
> - * unless we are using the system page size, in which case anonymous
> memory
> - * is OK. Use align as a hint for the page size.
> - * In this case, set MAP_NORESERVE to avoid allocating backing store
> memory.
> + * from the supplied fd, we should make sure to use the same page size,
> to
> + * this end we mmap the supplied fd. In this case, set MAP_NORESERVE to
> + * avoid allocating backing store memory.
> + * We do this unless we are using the system page size, in which case
> + * anonymous memory is OK.
> */
> int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 :
> fd;
> int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE;