[PATCH 3/3] --format=pretty: avoid calculating expensive expansions twice
- From
René Scharfe <rene.scharfe@lsrfire.ath.cx>
- Date
- Nov 10, 2007, 11:18 UTC
- Message-ID
- <47359382.1010600@lsrfire.ath.cx>
- In-Reply-To
- <20071110004635.GA14992@sigill.intra.peff.net>
As Jeff King remarked, format strings with duplicate placeholders can be slow to expand, because each instance is calculated anew.
This patch makes use of the fact that format_commit_message() and its helper functions only ever add stuff to the end of the strbuf. For certain expensive placeholders, store the offset and length of their expansion with the strbuf at the first occurrence. Later they expansion result can simply be copied from there -- no malloc() or strdup() required.
These certain placeholders are the abbreviated commit, tree and parent hashes, as the search for a unique abbreviated hash is quite costly. Here are the times for next (best of three runs):
$ time git log --pretty=format:%h >/dev/null
real 0m0.611s user 0m0.404s sys 0m0.204s
$ time git log --pretty=format:%h%h%h%h >/dev/null
real 0m1.206s user 0m0.744s sys 0m0.452s
And here those with this patch (and the previous two); the speedup of the single placeholder case is just noise:
$ time git log --pretty=format:%h >/dev/null
real 0m0.608s user 0m0.416s sys 0m0.192s
$ time git log --pretty=format:%h%h%h%h >/dev/null
real 0m0.639s user 0m0.488s sys 0m0.140s
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx> --- pretty.c | 32 ++++++++++++++++++++++++++++++++ 1 files changed, 32 insertions(+), 0 deletions(-)
diff --git a/pretty.c b/pretty.c index 0c2f83b..ab142b8 100644 --- a/pretty.c +++ b/pretty.c @@ -369,8 +369,30 @@ struct format_commit_context { struct chunk committer; struct chunk encoding; size_t body_off; + + /* The following ones are relative to the result struct strbuf. */ + struct chunk abbrev_commit_hash; + struct chunk abbrev_tree_hash; + struct chunk abbrev_parent_hashes; }; +static int add_again(struct strbuf *sb, struct chunk *chunk) +{ + if (chunk->len) { + strbuf_adddup(sb, chunk->off, chunk->len); + return 1; + } + + /* + * We haven't seen this chunk before. Our caller is surely + * going to add it the hard way now. Remember the most likely + * start of the to-be-added chunk: the current end of the + * struct strbuf. + */ + chunk->off = sb->len; + return 0; +} + static void parse_commit_header(struct format_commit_context *context) { const char *msg = context->commit->buffer; @@ -447,15 +469,21 @@ static void format_commit_item(struct strbuf *sb, const char *placeholder, strbuf_addstr(sb, sha1_to_hex(commit->object.sha1)); return; case 'h': /* abbreviated commit hash */ + if (add_again(sb, &c->abbrev_commit_hash)) + return; strbuf_addstr(sb, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV)); + c->abbrev_commit_hash.len = sb->len - c->abbrev_commit_hash.off; return; case 'T': /* tree hash */ strbuf_addstr(sb, sha1_to_hex(commit->tree->object.sha1)); return; case 't': /* abbreviated tree hash */ + if (add_again(sb, &c->abbrev_tree_hash)) + return; strbuf_addstr(sb, find_unique_abbrev(commit->tree->object.sha1, DEFAULT_ABBREV)); + c->abbrev_tree_hash.len = sb->len - c->abbrev_tree_hash.off; return; case 'P': /* parent hashes */ for (p = commit->parents; p; p = p->next) { @@ -465,12 +493,16 @@ static void format_commit_item(struct strbuf *sb, const char *placeholder, } return; case 'p': /* abbreviated parent hashes */ + if (add_again(sb, &c->abbrev_parent_hashes)) + return; for (p = commit->parents; p; p = p->next) { if (p != commit->parents) strbuf_addch(sb, ' '); strbuf_addstr(sb, find_unique_abbrev( p->item->object.sha1, DEFAULT_ABBREV)); } + c->abbrev_parent_hashes.len = sb->len - + c->abbrev_parent_hashes.off; return; case 'm': /* left/right/bottom */ strbuf_addch(sb, (commit->object.flags & BOUNDARY)
-- 1.5.3.5.1651.g30bf