"Shawn O. Pearce" <spearce@xxxxxxxxxxx> writes:
> Only on tags which are considered possible matches. What we do
> now is we walk back along the commit history until we find a commit
> which has a tag pointing at it. As soon as we find that commit we
> enqueue its corresponding tag into a list and completely ignore its
> parents, aborting listing any further back. So we really only pay
> the bare minimum price here.
This actually is QUITE bad.
With the tip of linux-2.6 repository, v1.4.4 series takes 0.03s
while v1.5.0-rc1 takes about 3.6s. That is 100x fold, not just
4x.
It turns out that to describe 0404f87f (tip of linux-2.6) the
new one picks up 61 tags in the posible-tag loop.
Since this loop uses the usual date-order, we can limit the
number of candidate tags without losing too much precision.
When limiting the candidates to only 6 (attached patch), the
time drops to 0.25s.
---
diff --git a/builtin-describe.c b/builtin-describe.c
index a8c98ce..a1ecec2 100644
--- a/builtin-describe.c
+++ b/builtin-describe.c
@@ -12,6 +12,7 @@ static const char describe_usage[] =
static int all; /* Default to annotated tags only */
static int tags; /* But allow any tags if --tags is specified */
+static int debug;
static int abbrev = DEFAULT_ABBREV;
@@ -113,6 +114,7 @@ static void describe(const char *arg, int last_one)
static int initialized = 0;
struct commit_name *n;
struct possible_tag *all_matches, *min_match, *cur_match;
+ int cnt;
if (get_sha1(arg, sha1))
die("Not a valid object name %s", arg);
@@ -136,6 +138,7 @@ static void describe(const char *arg, int last_one)
all_matches = NULL;
cur_match = NULL;
commit_list_insert(cmit, &list);
+ cnt = 6;
while (list) {
struct commit *c = pop_commit(&list);
n = match(c);
@@ -148,6 +151,8 @@ static void describe(const char *arg, int last_one)
else
all_matches = p;
cur_match = p;
+ if (--cnt <= 0)
+ break;
} else {
struct commit_list *parents = c->parents;
while (parents) {
@@ -161,6 +166,18 @@ static void describe(const char *arg, int last_one)
}
}
}
+ if (list)
+ free_commit_list(list);
+
+ if (debug) {
+ int cnt = 0;
+ for (cur_match = all_matches;
+ cur_match;
+ cur_match = cur_match->next)
+ cnt++;
+ fprintf(stderr, "%d candidates for %s\n", cnt,
+ sha1_to_hex(cmit->object.sha1));
+ }
if (!all_matches)
die("cannot describe '%s'", sha1_to_hex(cmit->object.sha1));
@@ -210,6 +227,8 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
all = 1;
else if (!strcmp(arg, "--tags"))
tags = 1;
+ else if (!strcmp(arg, "--debug"))
+ debug = 1;
else if (!strncmp(arg, "--abbrev=", 9)) {
abbrev = strtoul(arg + 9, NULL, 10);
if (abbrev < MINIMUM_ABBREV || 40 < abbrev)
-
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