>There are local complaints that filtering out only zero pages is slow. I
>found that is_zero_page was inefficient. It checks if the page contains any
>non-zero bytes - one byte at a time.
>
>Improve performance by checking for non-zero data 64 bits at a time.
>
>Did testing in x86_64 mode on an Intel Xeon x5560 system with 18GB RAM.
>Executed:
> time makedumpfile -d 1 /proc/vmcore <destination>
>
>The amount of time taken in User space was reduced by 64%. The total time to
>dump memory was reduced by 27%.
>
>Change Log:
>
>v1 => v2)
>
>o Eliminate loop unrolling as it is of minimal benefit based on CPU.
Thank you for fixing, I'll merge this into v1.5.6.
Atsushi Kumagai
>is_zero_page
>Signed-off-by: Marc Milgram <mmilgram at redhat.com>
>---
>diff --git a/makedumpfile.h b/makedumpfile.h
>index 3d270c6..1751e3a 100644
>--- a/makedumpfile.h
>+++ b/makedumpfile.h
>@@ -1634,9 +1634,11 @@ static inline int
> is_zero_page(unsigned char *buf, long page_size)
> {
> size_t i;
>+ unsigned long long *vect = (unsigned long long *) buf;
>+ long page_len = page_size / sizeof(unsigned long long);
>
>- for (i = 0; i < page_size; i++)
>- if (buf[i])
>+ for (i = 0; i < page_len; i++)
>+ if (vect[i])
> return FALSE;
> return TRUE;
> }
>
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