On Wed, 15 May 2013 13:43:59 -0500
Cliff Wickman <cpw at sgi.com> wrote:
> From: Cliff Wickman <cpw at sgi.com>
>
> Because addresses of each successive page structure are often descending
> it is much faster to use read()'s, so set off info->flag_usemmap
> while doing exclude_free_page().
>
> Signed-off-by: Cliff Wickman <cpw at sgi.com>
Sounds good.
BTW, do you have a speed measurement like your another patch ?
> I find this to speed the scan of page structures for a 1TB system from
> 60sec to 30sec.
Thanks
Atsushi Kumagai
> ---
> makedumpfile.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> Index: makedumpfile.mmap/makedumpfile.c
> ===================================================================
> --- makedumpfile.mmap.orig/makedumpfile.c
> +++ makedumpfile.mmap/makedumpfile.c
> @@ -3925,9 +3925,18 @@ _exclude_free_page(void)
> return TRUE;
> }
>
> +/*
> + * Note that this is a very lengthy process, even using mmap(2). The
> + * page structures in the free lists are read one-at-a-time, but using
> + * readpage_elf(), which reads an entire page. And addresses of each
> + * successive page structure are often descending, which means that each
> + * read is another mmap(2) operation.
> + * It is much faster to use read()'s, so set off info->flag_usemmap here.
> + */
> int
> exclude_free_page(void)
> {
> + int save = info->flag_usemmap;
> /*
> * Check having necessary information.
> */
> @@ -3961,8 +3970,12 @@ exclude_free_page(void)
> /*
> * Detect free pages and update 2nd-bitmap.
> */
> - if (!_exclude_free_page())
> + info->flag_usemmap = 0;
> + if (!_exclude_free_page()) {
> + info->flag_usemmap = save;
> return FALSE;
> + }
> + info->flag_usemmap = save;
>
> return TRUE;
> }
