When fast-export wants to export a blob object, it first
calls parse_object to get a "struct object" and check
whether we have already shown the object. If we haven't
shown it, we then use read_sha1_file to pull it from disk
and write it out.
That means we load each blob from disk twice: once for
parse_object to find its type and check its sha1, and a
second time when we actually output it. We can drop this to
a single load by using lookup_object to check the SHOWN
flag, and then checking the signature on and outputting a
single buffer.
This provides modest speedups on git.git (best-of-five, "git
fast-export HEAD >/dev/null"):
[before] [after]
real 0m14.347s real 0m13.780s
user 0m14.084s user 0m13.620s
sys 0m0.208s sys 0m0.100s
and somewhat more on more blob-heavy repos (this is a
repository full of media files):
[before] [after]
real 0m52.236s real 0m44.451s
user 0m50.568s user 0m43.000s
sys 0m1.536s sys 0m1.284s
Signed-off-by: Jeff King <p...@peff.net>
---
We actually spend a non-trivial amount of time re-checking the sha1 of
objects we are loading. This change also makes it easy to drop that
checking, though perhaps the additional safety is a good thing to have
during an export. The timings without it are:
git.git (was 14.347s)
real 0m11.452s
user 0m11.336s
sys 0m0.072s
photos (was 44.451s)
real 0m18.383s
user 0m17.108s
sys 0m1.224s
builtin/fast-export.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 3eba852..d380155 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -119,6 +119,7 @@ static void export_blob(const unsigned char *sha1)
enum object_type type;
char *buf;
struct object *object;
+ int eaten;
if (no_data)
return;
@@ -126,16 +127,18 @@ static void export_blob(const unsigned char *sha1)
if (is_null_sha1(sha1))
return;
- object = parse_object(sha1);
- if (!object)
- die ("Could not read blob %s", sha1_to_hex(sha1));
-
- if (object->flags & SHOWN)
+ object = lookup_object(sha1);
+ if (object && object->flags & SHOWN)
return;
buf = read_sha1_file(sha1, &type, &size);
if (!buf)
die ("Could not read blob %s", sha1_to_hex(sha1));
+ if (check_sha1_signature(sha1, buf, size, typename(type)) < 0)
+ die("sha1 mismatch in blob %s", sha1_to_hex(sha1));
+ object = parse_object_buffer(sha1, type, size, buf, &eaten);
+ if (!object)
+ die("Could not read blob %s", sha1_to_hex(sha1));
mark_next_object(object);
@@ -147,7 +150,8 @@ static void export_blob(const unsigned char *sha1)
show_progress();
object->flags |= SHOWN;
- free(buf);
+ if (!eaten)
+ free(buf);
}
static int depth_first(const void *a_, const void *b_)
--
1.8.2.rc2.7.gef06216
--
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