On Fri, May 30, 2014 at 10:35:14AM -0700, Junio C Hamano wrote:
> > Do you want me to roll it up with a real commit message?
>
> Yes. I think the change is sensible.
Here it is. We may want to make these helper functions available to
other callers so they can use the same trick, but I do not know offhand
of any others that would want it. pretty.c is the obvious place, and it
already uses a similar trick in logmsg_reencode (and I would expect most
users of the commit message would actually want the reencoded version,
and would use that).
-- >8 --
Subject: [PATCH] reuse commit->buffer when parsing signatures
When we call show_signature or show_mergetag, we read the
commit object fresh via read_sha1_file and reparse its
headers. However, in most cases we already have the object
data available as commit->buffer. This is partially
laziness in dealing with the memory allocation issues, but
partially defensive programming, in that we would always
want to verify a clean version of the buffer (not one that
might have been munged by other users of the commit).
However, we do not currently ever munge commit->buffer, and
not using the already-available buffer carries a fairly big
performance penalty when we are looking at a large number of
commits. Here are timings on linux.git:
[baseline, no signatures]
$ time git log >/dev/null
real 0m4.902s
user 0m4.784s
sys 0m0.120s
[before]
$ time git log --show-signature >/dev/null
real 0m14.735s
user 0m9.964s
sys 0m0.944s
[after]
$ time git log --show-signature >/dev/null
real 0m9.981s
user 0m5.260s
sys 0m0.936s
Note that our user CPU time drops almost in half, close to
the non-signature case, but we do still spend more
wall-clock and system time, presumably from dealing with
gpg.
An alternative to this is to note that most commits do not
have signatures (less than 1% in this repo), yet we pay the
re-parsing cost for every commit just to find out if it has
a mergetag or signature. If we checked that when parsing the
commit initially, we could avoid re-examining most commits
later on. Even if we did pursue that direction, however,
this would still speed up the cases where we _do_ have
signatures. So it's probably worth doing either way.
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
commit.c | 44 ++++++++++++++++++++++++++++++++++++--------
commit.h | 2 +-
log-tree.c | 2 +-
3 files changed, 38 insertions(+), 10 deletions(-)
diff --git a/commit.c b/commit.c
index f479331..9e2abf7 100644
--- a/commit.c
+++ b/commit.c
@@ -1080,14 +1080,42 @@ static int do_sign_commit(struct strbuf *buf, const char *keyid)
return 0;
}
-int parse_signed_commit(const unsigned char *sha1,
+/*
+ * Return the contents of the object pointed to by commit, as
+ * if read by read_sha1_file. However, in cases where the commit's
+ * data is already in memory, return that as an optimization.
+ *
+ * The resulting buffer may or may not be freshly allocated,
+ * and should only be freed by free_commit_buffer.
+ */
+static const char *read_commit_buffer(const struct commit *commit,
+ enum object_type *type,
+ unsigned long *size)
+{
+ if (commit->buffer) {
+ *type = OBJ_COMMIT;
+ *size = strlen(commit->buffer);
+ return commit->buffer;
+ }
+
+ return read_sha1_file(commit->object.sha1, type, size);
+}
+
+static void free_commit_buffer(const char *buffer, const struct commit *commit)
+{
+ if (buffer != commit->buffer)
+ free((char *)buffer);
+}
+
+int parse_signed_commit(const struct commit *commit,
struct strbuf *payload, struct strbuf *signature)
{
+
unsigned long size;
enum object_type type;
- char *buffer = read_sha1_file(sha1, &type, &size);
+ const char *buffer = read_commit_buffer(commit, &type, &size);
int in_signature, saw_signature = -1;
- char *line, *tail;
+ const char *line, *tail;
if (!buffer || type != OBJ_COMMIT)
goto cleanup;
@@ -1098,7 +1126,7 @@ int parse_signed_commit(const unsigned char *sha1,
saw_signature = 0;
while (line < tail) {
const char *sig = NULL;
- char *next = memchr(line, '\n', tail - line);
+ const char *next = memchr(line, '\n', tail - line);
next = next ? next + 1 : tail;
if (in_signature && line[0] == ' ')
@@ -1120,7 +1148,7 @@ int parse_signed_commit(const unsigned char *sha1,
line = next;
}
cleanup:
- free(buffer);
+ free_commit_buffer(buffer, commit);
return saw_signature;
}
@@ -1211,7 +1239,7 @@ void check_commit_signature(const struct commit* commit, struct signature_check
sigc->result = 'N';
- if (parse_signed_commit(commit->object.sha1,
+ if (parse_signed_commit(commit,
&payload, &signature) <= 0)
goto out;
status = verify_signed_buffer(payload.buf, payload.len,
@@ -1258,10 +1286,10 @@ struct commit_extra_header *read_commit_extra_headers(struct commit *commit,
struct commit_extra_header *extra = NULL;
unsigned long size;
enum object_type type;
- char *buffer = read_sha1_file(commit->object.sha1, &type, &size);
+ const char *buffer = read_commit_buffer(commit, &type, &size);
if (buffer && type == OBJ_COMMIT)
extra = read_commit_extra_header_lines(buffer, size, exclude);
- free(buffer);
+ free_commit_buffer(buffer, commit);
return extra;
}
diff --git a/commit.h b/commit.h
index a9f177b..a765f0f 100644
--- a/commit.h
+++ b/commit.h
@@ -287,7 +287,7 @@ struct merge_remote_desc {
*/
struct commit *get_merge_parent(const char *name);
-extern int parse_signed_commit(const unsigned char *sha1,
+extern int parse_signed_commit(const struct commit *commit,
struct strbuf *message, struct strbuf *signature);
extern void print_commit_list(struct commit_list *list,
const char *format_cur,
diff --git a/log-tree.c b/log-tree.c
index cf2f86c..6358599 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -376,7 +376,7 @@ static void show_signature(struct rev_info *opt, struct commit *commit)
struct strbuf gpg_output = STRBUF_INIT;
int status;
- if (parse_signed_commit(commit->object.sha1, &payload, &signature) <= 0)
+ if (parse_signed_commit(commit, &payload, &signature) <= 0)
goto out;
status = verify_signed_buffer(payload.buf, payload.len,
--
2.0.0.rc1.436.g03cb729
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