Subject: Re: [PATCH] update-index/diff-index: use core.preloadindex to improve performance

From: Karsten Blees <[email-masked]>
Date: Tue, 13 Nov 2012 22:51:46 +0100

Am 13.11.2012 17:46, schrieb Junio C Hamano:
> [email-masked] writes:
> 
> If anything, "fix your mailer" probably is the policy you are
> looking for, I think.

Well then...I've cloned myself @gmail, I hope this is better.

Just some provoking thoughts...(if I may):

RFC-5322 recommends wrapping lines at 78, and mail relays and gateways are allowed to change message content according to the capabilities of the receiver (RFC-5598). In essence, plaintext mail is completely unsuitable for preformatted text such as source code.

On the other hand, git tries to solve the very problem of distributed source code management, and consistency by strong sha-1 checksums is on the top of the feature list.

It is somehow hard to believe that contributing to git itself should only be possible using the most unreliable of protocols. Don't you trust your own software?

-- >8 --
Subject: [PATCH] update-index/diff-index: use core.preloadindex to improve performance

'update-index --refresh' and 'diff-index' (without --cached) don't honor
the core.preloadindex setting yet. Porcelain commands using these (such as
git [svn] rebase) suffer from this, especially on Windows.

Use read_cache_preload to improve performance.

Additionally, in builtin/diff.c, don't preload index status if we don't
access the working copy (--cached).

Results with msysgit on WebKit repo (2GB in 200k files):

                | update-index | diff-index | rebase
----------------+--------------+------------+---------
msysgit-v1.8.0  |       9.157s |    10.536s | 42.791s
+ preloadindex  |       9.157s |    10.536s | 28.725s
+ this patch    |       2.329s |     2.752s | 15.152s
+ fscache [1]   |       0.731s |     1.171s |  8.877s

[1] https://github.com/kblees/git/tree/kb/fscache-v3

Thanks-to: Albert Krawczyk <[email-masked]>
Signed-off-by: Karsten Blees <[email-masked]>
---

Can also be pulled from: https://github.com/kblees/git/tree/kb/update-diff-index-preload-upstream

More performance figures (for msysgit) can be found in this discussion: https://github.com/pro-logic/git/commit/32c03dd8

 builtin/diff-index.c   |  8 ++++++--
 builtin/diff.c         | 12 ++++++++----
 builtin/update-index.c |  1 +
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/builtin/diff-index.c b/builtin/diff-index.c
index 2eb32bd..1c737f7 100644
--- a/builtin/diff-index.c
+++ b/builtin/diff-index.c
@@ -41,9 +41,13 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	if (rev.pending.nr != 1 ||
 	    rev.max_count != -1 || rev.min_age != -1 || rev.max_age != -1)
 		usage(diff_cache_usage);
-	if (!cached)
+	if (!cached) {
 		setup_work_tree();
-	if (read_cache() < 0) {
+		if (read_cache_preload(rev.diffopt.pathspec.raw) < 0) {
+			perror("read_cache_preload");
+			return -1;
+		}
+	} else if (read_cache() < 0) {
 		perror("read_cache");
 		return -1;
 	}
diff --git a/builtin/diff.c b/builtin/diff.c
index 9650be2..198b921 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -130,8 +130,6 @@ static int builtin_diff_index(struct rev_info *revs,
 			usage(builtin_diff_usage);
 		argv++; argc--;
 	}
-	if (!cached)
-		setup_work_tree();
 	/*
 	 * Make sure there is one revision (i.e. pending object),
 	 * and there is no revision filtering parameters.
@@ -140,8 +138,14 @@ static int builtin_diff_index(struct rev_info *revs,
 	    revs->max_count != -1 || revs->min_age != -1 ||
 	    revs->max_age != -1)
 		usage(builtin_diff_usage);
-	if (read_cache_preload(revs->diffopt.pathspec.raw) < 0) {
-		perror("read_cache_preload");
+	if (!cached) {
+		setup_work_tree();
+		if (read_cache_preload(revs->diffopt.pathspec.raw) < 0) {
+			perror("read_cache_preload");
+			return -1;
+		}
+	} else if (read_cache() < 0) {
+		perror("read_cache");
 		return -1;
 	}
 	return run_diff_index(revs, cached);
diff --git a/builtin/update-index.c b/builtin/update-index.c
index 74986bf..ada1dff 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -593,6 +593,7 @@ struct refresh_params {
 static int refresh(struct refresh_params *o, unsigned int flag)
 {
 	setup_work_tree();
+	read_cache_preload(NULL);
 	*o->has_errors |= refresh_cache(o->flags | flag);
 	return 0;
 }
-- 
1.8.0.msysgit.0.3.g7d9d98c

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