The loose objects cache is filled one subdirectory at a time as needed.
It is stored in an oid_array, which has to be resorted after each add
operation. So when querying a wide range of objects, the partially
filled array needs to be resorted up to 255 times, which takes over 100
times longer than sorting once.
Use one oid_array for each subdirectory. This ensures that entries have
to only be sorted a single time. It also avoids eight binary search
steps for each cache lookup as a small bonus.
The cache is used for collision checks for the log placeholders %h, %t
and %p, and we can see the change speeding them up in a repository with
ca. 100 objects per subdirectory:
$ git count-objects
26733 objects, 68808 kilobytes
Test HEAD^ HEAD
--------------------------------------------------------------------
4205.1: log with %H 0.51(0.47+0.04) 0.51(0.49+0.02) +0.0%
4205.2: log with %h 0.84(0.82+0.02) 0.60(0.57+0.03) -28.6%
4205.3: log with %T 0.53(0.49+0.04) 0.52(0.48+0.03) -1.9%
4205.4: log with %t 0.84(0.80+0.04) 0.60(0.59+0.01) -28.6%
4205.5: log with %P 0.52(0.48+0.03) 0.51(0.50+0.01) -1.9%
4205.6: log with %p 0.85(0.78+0.06) 0.61(0.56+0.05) -28.2%
4205.7: log with %h-%h-%h 0.96(0.92+0.03) 0.69(0.64+0.04) -28.1%
Reported-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
Signed-off-by: Rene Scharfe <l.s.r@xxxxxx>
---
object-store.h | 2 +-
sha1-file.c | 9 ++++++---
2 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/object-store.h b/object-store.h
index 709bf856b6..2fb6c0e4db 100644
--- a/object-store.h
+++ b/object-store.h
@@ -20,7 +20,7 @@ struct object_directory {
* Be sure to call odb_load_loose_cache() before using.
*/
char loose_objects_subdir_seen[256];
- struct oid_array loose_objects_cache;
+ struct oid_array loose_objects_cache[256];
/*
* Path to the alternative object store. If this is a relative path,
diff --git a/sha1-file.c b/sha1-file.c
index 2f965b2688..c3c6e50704 100644
--- a/sha1-file.c
+++ b/sha1-file.c
@@ -2155,7 +2155,7 @@ struct oid_array *odb_loose_cache(struct object_directory *odb,
{
int subdir_nr = oid->hash[0];
odb_load_loose_cache(odb, subdir_nr);
- return &odb->loose_objects_cache;
+ return &odb->loose_objects_cache[subdir_nr];
}
void odb_load_loose_cache(struct object_directory *odb, int subdir_nr)
@@ -2173,14 +2173,17 @@ void odb_load_loose_cache(struct object_directory *odb, int subdir_nr)
for_each_file_in_obj_subdir(subdir_nr, &buf,
append_loose_object,
NULL, NULL,
- &odb->loose_objects_cache);
+ &odb->loose_objects_cache[subdir_nr]);
odb->loose_objects_subdir_seen[subdir_nr] = 1;
strbuf_release(&buf);
}
void odb_clear_loose_cache(struct object_directory *odb)
{
- oid_array_clear(&odb->loose_objects_cache);
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(odb->loose_objects_cache); i++)
+ oid_array_clear(&odb->loose_objects_cache[i]);
memset(&odb->loose_objects_subdir_seen, 0,
sizeof(odb->loose_objects_subdir_seen));
}
--
2.20.1
