fsck: use oidset instead of oid_array for skipList

Change the implementation of the skipList feature to use oidset
instead of oid_array to store SHA-1s for later lookup.

This list is parsed once on startup by fsck, fetch-pack or
receive-pack depending on the *.skipList config in use. I.e. only once
per invocation, but note that for "clone --recurse-submodules" each
submodule will re-parse the list, in addition to the main project, and
it will be re-parsed when checking .gitmodules blobs, see
fb16287719 ("fsck: check skiplist for object in fsck_blob()",
2018-06-27).

Memory usage is a bit higher, but we don't need to keep track of the
sort order anymore. Embed the oidset into struct fsck_options to make
its ownership clear (no hidden sharing) and avoid unnecessary pointer
indirection.

The cumulative impact on performance of this & the preceding change,
using the test setup described in the previous commit:

    Test                                             HEAD~2            HEAD~                   HEAD
    ----------------------------------------------------------------------------------------------------------------
    1450.3: fsck with 0 skipped bad commits          7.70(7.31+0.38)   7.72(7.33+0.38) +0.3%   7.70(7.30+0.40) +0.0%
    1450.5: fsck with 1 skipped bad commits          7.84(7.47+0.37)   7.69(7.32+0.36) -1.9%   7.71(7.29+0.41) -1.7%
    1450.7: fsck with 10 skipped bad commits         7.81(7.40+0.40)   7.94(7.57+0.36) +1.7%   7.92(7.55+0.37) +1.4%
    1450.9: fsck with 100 skipped bad commits        7.81(7.42+0.38)   7.95(7.53+0.41) +1.8%   7.83(7.42+0.41) +0.3%
    1450.11: fsck with 1000 skipped bad commits      7.99(7.62+0.36)   7.90(7.50+0.40) -1.1%   7.86(7.49+0.37) -1.6%
    1450.13: fsck with 10000 skipped bad commits     7.98(7.57+0.40)   7.94(7.53+0.40) -0.5%   7.90(7.45+0.44) -1.0%
    1450.15: fsck with 100000 skipped bad commits    7.97(7.57+0.39)   8.03(7.67+0.36) +0.8%   7.84(7.43+0.41) -1.6%
    1450.17: fsck with 1000000 skipped bad commits   7.72(7.22+0.50)   7.28(7.07+0.20) -5.7%   7.13(6.87+0.25) -7.6%

Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 21 deletions

diff --git a/fsck.c b/fsck.c
index 972a26b9ba..4c643f1d40 100644
--- a/fsck.c
+++ b/fsck.c
@@ -10,7 +10,6 @@
 #include "fsck.h"
 #include "refs.h"
 #include "utf8.h"
-#include "sha1-array.h"
 #include "decorate.h"
 #include "oidset.h"
 #include "packfile.h"
@@ -182,19 +181,10 @@ static int fsck_msg_type(enum fsck_msg_id msg_id,
 
 static void init_skiplist(struct fsck_options *options, const char *path)
 {
-	static struct oid_array skiplist = OID_ARRAY_INIT;
-	int sorted;
 	FILE *fp;
 	struct strbuf sb = STRBUF_INIT;
 	struct object_id oid;
 
-	if (options->skiplist)
-		sorted = options->skiplist->sorted;
-	else {
-		sorted = 1;
-		options->skiplist = &skiplist;
-	}
-
 	fp = fopen(path, "r");
 	if (!fp)
 		die("Could not open skip list: %s", path);
@@ -202,19 +192,12 @@ static void init_skiplist(struct fsck_options *options, const char *path)
 		const char *p;
 		if (parse_oid_hex(sb.buf, &oid, &p) || *p != '\0')
 			die("Invalid SHA-1: %s", sb.buf);
-		oid_array_append(&skiplist, &oid);
-		if (sorted && skiplist.nr > 1 &&
-				oidcmp(&skiplist.oid[skiplist.nr - 2],
-				       &oid) > 0)
-			sorted = 0;
+		oidset_insert(&options->skiplist, &oid);
 	}
 	if (ferror(fp))
 		die_errno("Could not read '%s'", path);
 	fclose(fp);
 	strbuf_release(&sb);
-
-	if (sorted)
-		skiplist.sorted = 1;
 }
 
 static int parse_msg_type(const char *str)
@@ -319,9 +302,7 @@ static void append_msg_id(struct strbuf *sb, const char *msg_id)
 
 static int object_on_skiplist(struct fsck_options *opts, struct object *obj)
 {
-	if (opts && opts->skiplist && obj)
-		return oid_array_lookup(opts->skiplist, &obj->oid) >= 0;
-	return 0;
+	return opts && obj && oidset_contains(&opts->skiplist, &obj->oid);
 }
 
 __attribute__((format (printf, 4, 5)))