On 02/02/2012 02:39 AM, Steven Lang wrote:
> In looking at profiling the speed of fill_pattern(), it calls memcpy()
> for the fill pattern repeatedly for multibyte patterns. So for a 4
> byte pattern with 8k IO, it calls memcpy() 2048 times.
>
> Since there is already 512 bytes reserved for the pattern, I figured a
> simple solution was to use it. This patch replicates short patterns
> so they can be more efficiently copied. (Single byte patterns are
> left alone since they can make use of the much more efficient memset()
> call.)
>
> The result is a 10x performance improvement on pattern filling. (With
> this patch, it's still 3x slower than when it re-uses the already
> filled pattern.)
>
> ---
> options.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/options.c b/options.c
> index f9bd1a4..b6989d4 100644
> --- a/options.c
> +++ b/options.c
> @@ -689,6 +689,10 @@ static int str_verify_pattern_cb(void *data,
> const char *input)
> }
> }
> }
> + while (i > 1 && i * 2 <= MAX_PATTERN_SIZE) {
> + memcpy(&td->o.verify_pattern[i], &td->o.verify_pattern[0], i);
> + i *= 2;
> + }
> td->o.verify_pattern_bytes = i;
> /*
> * VERIFY_META could already be set
Looks like you are missing the interesting part of this patch :-)
But the idea definitely sounds good.
--
Jens Axboe
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