Hi,
On 03/16, Andreas Krey wrote:
> get_ref_cache used a linear list, which obviously is O(n^2).
> Use a fixed bucket hash which just takes a factor of 100000
> (~ 317^2) out of the n^2 - which is enough.
>
> Signed-off-by: Andreas Krey <[email protected]>
> ---
>
> This brings 'git clean -ndx' times down from 17 minutes
> to 11 seconds on one of our workspaces (which accumulated
> a lot of ignored directories). Actuallly using adaptive
> hashing or other structures seems overkill.
>
> refs.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/refs.c b/refs.c
> index e23542b..8198d9e 100644
> --- a/refs.c
> +++ b/refs.c
> @@ -982,6 +982,8 @@ struct packed_ref_cache {
> struct stat_validity validity;
> };
>
> +#define REF_CACHE_HASH 317
> +
> /*
> * Future: need to be in "struct repository"
> * when doing a full libification.
> @@ -996,7 +998,7 @@ static struct ref_cache {
> * is initialized correctly.
> */
> char name[1];
> -} ref_cache, *submodule_ref_caches;
> +} ref_cache, *submodule_ref_caches[REF_CACHE_HASH];
>
> /* Lock used for the main packed-refs file: */
> static struct lock_file packlock;
> @@ -1065,18 +1067,19 @@ static struct ref_cache *create_ref_cache(const char
> *submodule)
> */
> static struct ref_cache *get_ref_cache(const char *submodule)
> {
> - struct ref_cache *refs;
> + struct ref_cache *refs, **bucketp;
> + bucketp = submodule_ref_caches + strhash(submodule) % REF_CACHE_HASH;
>
This breaks the test-suite for me, in the cases where submodule is
NULL. How about something like this on top?
diff --git a/refs.c b/refs.c
index 8198d9e..311faf2 100644
--- a/refs.c
+++ b/refs.c
@@ -1068,7 +1068,9 @@ static struct ref_cache *create_ref_cache(const char
*submodule)
static struct ref_cache *get_ref_cache(const char *submodule)
{
struct ref_cache *refs, **bucketp;
- bucketp = submodule_ref_caches + strhash(submodule) % REF_CACHE_HASH;
+ bucketp = submodule_ref_caches;
+ if (submodule)
+ bucketp += strhash(submodule) % REF_CACHE_HASH;
if (!submodule || !*submodule)
return &ref_cache;
> if (!submodule || !*submodule)
> return &ref_cache;
>
> - for (refs = submodule_ref_caches; refs; refs = refs->next)
> + for (refs = *bucketp; refs; refs = refs->next)
> if (!strcmp(submodule, refs->name))
> return refs;
>
> refs = create_ref_cache(submodule);
> - refs->next = submodule_ref_caches;
> - submodule_ref_caches = refs;
> + refs->next = *bucketp;
> + *bucketp = refs;
> return refs;
> }
>
> --
> 2.3.2.223.g7a9409c
> --
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