Subject: Re: [PATCH 2/2] ls-files: move only kept cache entries in prune_cache()

From: Brandon Williams <[email-masked]>
Date: Fri, 10 Feb 2017 14:51:56 -0800

On 02/10, René Scharfe wrote:
> prune_cache() first identifies those entries at the start of the sorted
> array that can be discarded.  Then it moves the rest of the entries up.
> Last it identifies the unwanted trailing entries among the moved ones
> and cuts them off.
> 
> Change the order: Identify both start *and* end of the range to keep
> first and then move only those entries to the top.  The resulting code
> is slightly shorter and a bit more efficient.
> 
> Signed-off-by: Rene Scharfe <[email-masked]>
> ---
> The performance impact is probably only measurable with a *really* big
> index.

Well there's been a lot of talk recently about *really* big indexes, so
I'm sure someone out there will be happy :)

> 
>  builtin/ls-files.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/builtin/ls-files.c b/builtin/ls-files.c
> index 18105ec7ea..1c0f057d02 100644
> --- a/builtin/ls-files.c
> +++ b/builtin/ls-files.c
> @@ -379,10 +379,7 @@ static void prune_cache(const char *prefix, size_t prefixlen)
>  	pos = cache_name_pos(prefix, prefixlen);
>  	if (pos < 0)
>  		pos = -pos-1;
> -	memmove(active_cache, active_cache + pos,
> -		(active_nr - pos) * sizeof(struct cache_entry *));
> -	active_nr -= pos;
> -	first = 0;
> +	first = pos;
>  	last = active_nr;
>  	while (last > first) {
>  		int next = (last + first) >> 1;
> @@ -393,7 +390,9 @@ static void prune_cache(const char *prefix, size_t prefixlen)
>  		}
>  		last = next;
>  	}
> -	active_nr = last;
> +	memmove(active_cache, active_cache + pos,
> +		(last - pos) * sizeof(struct cache_entry *));
> +	active_nr = last - pos;
>  }
>  
>  /*
> -- 
> 2.11.1
> 

Both these patches look good to me.

-- 
Brandon Williams