Re: [PATCH] refs.c: get_ref_cache: use a bucket hash
- From
Thomas Gummerer <t.gummerer@gmail.com>
- Date
- Mar 16, 2015, 17:19 UTC
- Message-ID
- <20150316171909.GA8618@hank>
- In-Reply-To
- <20150316142026.GJ7847@inner.h.apk.li>
Hi,
On 03/16, Andreas Krey wrote:
Show 45 quoted lines
> 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 <a.krey@gmx.de>
> ---
>
> 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 > -- > To unsubscribe from this list: send the line "unsubscribe git" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html