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From: Taylor Blau <me@ttaylorr.com>
To: git@vger.kernel.org
Cc: avarab@gmail.com, dstolee@microsoft.com, gitster@pobox.com,
	jonathantanmy@google.com, peff@peff.net
Subject: [PATCH v3 16/16] midx.c: improve cache locality in midx_pack_order_cmp()
Date: Thu, 11 Mar 2021 12:05:42 -0500	[thread overview]
Message-ID: <550e785f10ba14f166958501c007b75a04052a0d.1615482270.git.me@ttaylorr.com> (raw)
In-Reply-To: <cover.1615482270.git.me@ttaylorr.com>

From: Jeff King <peff@peff.net>

There is a lot of pointer dereferencing in the pre-image version of
'midx_pack_order_cmp()', which this patch gets rid of.

Instead of comparing the pack preferred-ness and then the pack id, both
of these checks are done at the same time by using the high-order bit of
the pack id to represent whether it's preferred. Then the pack id and
offset are compared as usual.

This produces the same result so long as there are less than 2^31 packs,
which seems like a likely assumption to make in practice.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 midx.c | 55 +++++++++++++++++++++++++++++--------------------------
 1 file changed, 29 insertions(+), 26 deletions(-)

diff --git a/midx.c b/midx.c
index eea9574d92..4835cc13d1 100644
--- a/midx.c
+++ b/midx.c
@@ -828,46 +828,49 @@ static int write_midx_large_offsets(struct hashfile *f,
 	return 0;
 }
 
-static int midx_pack_order_cmp(const void *va, const void *vb, void *_ctx)
+struct midx_pack_order_data {
+	uint32_t nr;
+	uint32_t pack;
+	off_t offset;
+};
+
+static int midx_pack_order_cmp(const void *va, const void *vb)
 {
-	struct write_midx_context *ctx = _ctx;
-
-	struct pack_midx_entry *a = &ctx->entries[*(const uint32_t *)va];
-	struct pack_midx_entry *b = &ctx->entries[*(const uint32_t *)vb];
-
-	uint32_t perm_a = ctx->pack_perm[a->pack_int_id];
-	uint32_t perm_b = ctx->pack_perm[b->pack_int_id];
-
-	/* Sort objects in the preferred pack ahead of any others. */
-	if (a->preferred > b->preferred)
+	const struct midx_pack_order_data *a = va, *b = vb;
+	if (a->pack < b->pack)
 		return -1;
-	if (a->preferred < b->preferred)
+	else if (a->pack > b->pack)
 		return 1;
-
-	/* Then, order objects by which packs they appear in. */
-	if (perm_a < perm_b)
+	else if (a->offset < b->offset)
 		return -1;
-	if (perm_a > perm_b)
+	else if (a->offset > b->offset)
 		return 1;
-
-	/* Then, disambiguate by their offset within each pack. */
-	if (a->offset < b->offset)
-		return -1;
-	if (a->offset > b->offset)
-		return 1;
-
-	return 0;
+	else
+		return 0;
 }
 
 static uint32_t *midx_pack_order(struct write_midx_context *ctx)
 {
+	struct midx_pack_order_data *data;
 	uint32_t *pack_order;
 	uint32_t i;
 
+	ALLOC_ARRAY(data, ctx->entries_nr);
+	for (i = 0; i < ctx->entries_nr; i++) {
+		struct pack_midx_entry *e = &ctx->entries[i];
+		data[i].nr = i;
+		data[i].pack = ctx->pack_perm[e->pack_int_id];
+		if (!e->preferred)
+			data[i].pack |= (1U << 31);
+		data[i].offset = e->offset;
+	}
+
+	QSORT(data, ctx->entries_nr, midx_pack_order_cmp);
+
 	ALLOC_ARRAY(pack_order, ctx->entries_nr);
 	for (i = 0; i < ctx->entries_nr; i++)
-		pack_order[i] = i;
-	QSORT_S(pack_order, ctx->entries_nr, midx_pack_order_cmp, ctx);
+		pack_order[i] = data[i].nr;
+	free(data);
 
 	return pack_order;
 }
-- 
2.30.0.667.g81c0cbc6fd

  parent reply	other threads:[~2021-03-11 17:06 UTC|newest]

Thread overview: 171+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-10 23:02 [PATCH 0/9] midx: implement a multi-pack reverse index Taylor Blau
2021-02-10 23:02 ` [PATCH 1/9] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-02-11  2:27   ` Derrick Stolee
2021-02-11  2:34     ` Taylor Blau
2021-02-10 23:02 ` [PATCH 2/9] midx: allow marking a pack as preferred Taylor Blau
2021-02-11 19:33   ` SZEDER Gábor
2021-02-15 15:49     ` Taylor Blau
2021-02-15 17:01       ` Ævar Arnfjörð Bjarmason
2021-02-15 18:41         ` [PATCH 0/5] commit-graph: parse_options() cleanup Ævar Arnfjörð Bjarmason
2021-02-15 18:41         ` [PATCH 1/5] commit-graph: define common usage with a macro Ævar Arnfjörð Bjarmason
2021-02-16 11:33           ` Derrick Stolee
2021-02-15 18:41         ` [PATCH 2/5] commit-graph: remove redundant handling of -h Ævar Arnfjörð Bjarmason
2021-02-16 11:35           ` Derrick Stolee
2021-02-15 18:41         ` [PATCH 3/5] commit-graph: use parse_options_concat() Ævar Arnfjörð Bjarmason
2021-02-15 18:51           ` Taylor Blau
2021-02-15 19:53             ` Taylor Blau
2021-02-15 20:39             ` Ævar Arnfjörð Bjarmason
2021-09-17 21:13               ` SZEDER Gábor
2021-09-17 22:03                 ` Jeff King
2021-09-18  4:30                   ` Taylor Blau
2021-09-18  7:20                     ` Ævar Arnfjörð Bjarmason
2021-09-18 15:56                       ` Taylor Blau
2021-09-18 15:58                         ` Taylor Blau
2021-09-18  0:58                 ` Ævar Arnfjörð Bjarmason
2021-02-15 18:41         ` [PATCH 4/5] commit-graph: refactor dispatch loop for style Ævar Arnfjörð Bjarmason
2021-02-15 18:53           ` Taylor Blau
2021-02-16 11:40             ` Derrick Stolee
2021-02-16 12:02               ` Ævar Arnfjörð Bjarmason
2021-02-16 18:28                 ` Derrick Stolee
2021-02-15 18:41         ` [PATCH 5/5] commit-graph: show usage on "commit-graph [write|verify] garbage" Ævar Arnfjörð Bjarmason
2021-02-15 19:06           ` Taylor Blau
2021-02-16 11:43           ` Derrick Stolee
2021-02-15 21:01         ` [PATCH v2 0/4] midx: split out sub-commands Taylor Blau
2021-02-15 21:01           ` [PATCH v2 1/4] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-02-15 21:01           ` [PATCH v2 2/4] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-02-15 21:39             ` Ævar Arnfjörð Bjarmason
2021-02-15 21:45               ` Taylor Blau
2021-02-16 11:47                 ` Derrick Stolee
2021-02-15 21:01           ` [PATCH v2 3/4] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-02-15 21:01           ` [PATCH v2 4/4] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-02-15 21:54             ` Ævar Arnfjörð Bjarmason
2021-02-15 22:34               ` Taylor Blau
2021-02-15 23:11                 ` Ævar Arnfjörð Bjarmason
2021-02-15 23:49                   ` Taylor Blau
2021-02-16 11:50           ` [PATCH v2 0/4] midx: split out sub-commands Derrick Stolee
2021-02-16 14:28             ` Taylor Blau
2021-02-10 23:02 ` [PATCH 3/9] midx: don't free midx_name early Taylor Blau
2021-02-10 23:02 ` [PATCH 4/9] midx: keep track of the checksum Taylor Blau
2021-02-11  2:33   ` Derrick Stolee
2021-02-11  2:35     ` Taylor Blau
2021-02-10 23:03 ` [PATCH 5/9] midx: make some functions non-static Taylor Blau
2021-02-10 23:03 ` [PATCH 6/9] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-02-11  2:48   ` Derrick Stolee
2021-02-11  3:03     ` Taylor Blau
2021-02-10 23:03 ` [PATCH 7/9] pack-revindex: read " Taylor Blau
2021-02-11  2:53   ` Derrick Stolee
2021-02-11  3:04     ` Taylor Blau
2021-02-11  7:54   ` Junio C Hamano
2021-02-11 14:54     ` Taylor Blau
2021-02-10 23:03 ` [PATCH 8/9] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-02-10 23:03 ` [PATCH 9/9] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-02-11  2:58 ` [PATCH 0/9] midx: implement a multi-pack reverse index Derrick Stolee
2021-02-11  3:06   ` Taylor Blau
2021-02-11  8:13 ` Junio C Hamano
2021-02-11 18:37   ` Derrick Stolee
2021-02-11 18:55     ` Junio C Hamano
2021-02-24 19:09 ` [PATCH v2 00/15] " Taylor Blau
2021-02-24 19:09   ` [PATCH v2 01/15] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-02-24 19:09   ` [PATCH v2 02/15] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-02-24 19:09   ` [PATCH v2 03/15] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-02-24 19:09   ` [PATCH v2 04/15] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-03-02  4:06     ` Jonathan Tan
2021-03-02 19:02       ` Taylor Blau
2021-03-04  1:54         ` Jonathan Tan
2021-03-04  3:02           ` Taylor Blau
2021-02-24 19:09   ` [PATCH v2 05/15] builtin/multi-pack-index.c: don't enter bogus cmd_mode Taylor Blau
2021-02-24 19:09   ` [PATCH v2 06/15] builtin/multi-pack-index.c: display usage on unrecognized command Taylor Blau
2021-02-24 19:09   ` [PATCH v2 07/15] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-02-24 19:09   ` [PATCH v2 08/15] midx: allow marking a pack as preferred Taylor Blau
2021-03-02  4:17     ` Jonathan Tan
2021-03-02 19:09       ` Taylor Blau
2021-03-04  2:00         ` Jonathan Tan
2021-03-04  3:04           ` Taylor Blau
2021-02-24 19:09   ` [PATCH v2 09/15] midx: don't free midx_name early Taylor Blau
2021-02-24 19:10   ` [PATCH v2 10/15] midx: keep track of the checksum Taylor Blau
2021-02-24 19:10   ` [PATCH v2 11/15] midx: make some functions non-static Taylor Blau
2021-02-24 19:10   ` [PATCH v2 12/15] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-03-02  4:21     ` Jonathan Tan
2021-03-02  4:36       ` Taylor Blau
2021-03-02 19:15       ` Taylor Blau
2021-03-04  2:03         ` Jonathan Tan
2021-02-24 19:10   ` [PATCH v2 13/15] pack-revindex: read " Taylor Blau
2021-03-02 18:36     ` Jonathan Tan
2021-03-03 15:27       ` Taylor Blau
2021-02-24 19:10   ` [PATCH v2 14/15] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-02-24 19:10   ` [PATCH v2 15/15] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-03-02 18:40     ` Jonathan Tan
2021-03-03 15:30       ` Taylor Blau
2021-03-04  2:04         ` Jonathan Tan
2021-03-04  3:06           ` Taylor Blau
2021-03-11 17:04 ` [PATCH v3 00/16] midx: implement a multi-pack reverse index Taylor Blau
2021-03-11 17:04   ` [PATCH v3 01/16] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-03-29 11:20     ` Jeff King
2021-03-11 17:04   ` [PATCH v3 02/16] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-03-29 11:22     ` Jeff King
2021-03-11 17:04   ` [PATCH v3 03/16] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-03-11 17:04   ` [PATCH v3 04/16] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-03-29 11:36     ` Jeff King
2021-03-29 20:38       ` Taylor Blau
2021-03-30  7:04         ` Jeff King
2021-03-11 17:04   ` [PATCH v3 05/16] builtin/multi-pack-index.c: don't enter bogus cmd_mode Taylor Blau
2021-03-11 17:04   ` [PATCH v3 06/16] builtin/multi-pack-index.c: display usage on unrecognized command Taylor Blau
2021-03-29 11:42     ` Jeff King
2021-03-29 20:41       ` Taylor Blau
2021-03-11 17:05   ` [PATCH v3 07/16] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-03-11 17:05   ` [PATCH v3 08/16] midx: allow marking a pack as preferred Taylor Blau
2021-03-29 12:00     ` Jeff King
2021-03-29 21:15       ` Taylor Blau
2021-03-30  7:11         ` Jeff King
2021-03-11 17:05   ` [PATCH v3 09/16] midx: don't free midx_name early Taylor Blau
2021-03-11 17:05   ` [PATCH v3 10/16] midx: keep track of the checksum Taylor Blau
2021-03-11 17:05   ` [PATCH v3 11/16] midx: make some functions non-static Taylor Blau
2021-03-11 17:05   ` [PATCH v3 12/16] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-03-29 12:12     ` Jeff King
2021-03-29 21:22       ` Taylor Blau
2021-03-11 17:05   ` [PATCH v3 13/16] pack-revindex: read " Taylor Blau
2021-03-29 12:43     ` Jeff King
2021-03-29 21:27       ` Taylor Blau
2021-03-11 17:05   ` [PATCH v3 14/16] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-03-11 17:05   ` [PATCH v3 15/16] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-03-29 12:53     ` Jeff King
2021-03-29 21:30       ` Taylor Blau
2021-03-11 17:05   ` Taylor Blau [this message]
2021-03-29 12:59     ` [PATCH v3 16/16] midx.c: improve cache locality in midx_pack_order_cmp() Jeff King
2021-03-29 21:34       ` Taylor Blau
2021-03-30  7:15         ` Jeff King
2021-03-12 15:16   ` [PATCH v3 00/16] midx: implement a multi-pack reverse index Derrick Stolee
2021-03-29 13:05   ` Jeff King
2021-03-29 21:30     ` Junio C Hamano
2021-03-29 21:37     ` Taylor Blau
2021-03-30  7:15       ` Jeff King
2021-03-30 13:37         ` Taylor Blau
2021-03-30 15:03 ` [PATCH v4 " Taylor Blau
2021-03-30 15:03   ` [PATCH v4 01/16] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-03-30 15:03   ` [PATCH v4 02/16] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-03-30 15:03   ` [PATCH v4 03/16] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-03-30 15:03   ` [PATCH v4 04/16] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-03-30 15:04   ` [PATCH v4 05/16] builtin/multi-pack-index.c: don't enter bogus cmd_mode Taylor Blau
2021-03-30 15:04   ` [PATCH v4 06/16] builtin/multi-pack-index.c: display usage on unrecognized command Taylor Blau
2021-03-30 15:04   ` [PATCH v4 07/16] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-03-30 15:04   ` [PATCH v4 08/16] midx: allow marking a pack as preferred Taylor Blau
2021-04-01  0:32     ` Taylor Blau
2021-03-30 15:04   ` [PATCH v4 09/16] midx: don't free midx_name early Taylor Blau
2021-03-30 15:04   ` [PATCH v4 10/16] midx: keep track of the checksum Taylor Blau
2021-03-30 15:04   ` [PATCH v4 11/16] midx: make some functions non-static Taylor Blau
2021-03-30 15:04   ` [PATCH v4 12/16] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-03-30 15:04   ` [PATCH v4 13/16] pack-revindex: read " Taylor Blau
2021-03-30 15:04   ` [PATCH v4 14/16] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-09-08  1:08     ` [PATCH] pack-write: skip *.rev work when not writing *.rev Ævar Arnfjörð Bjarmason
2021-09-08  1:35       ` Carlo Arenas
2021-09-08  2:42         ` Taylor Blau
2021-09-08 15:47           ` Junio C Hamano
2021-09-08  2:50       ` Taylor Blau
2021-09-08  3:50         ` Taylor Blau
2021-09-08 10:18           ` Ævar Arnfjörð Bjarmason
2021-09-08 16:32             ` Taylor Blau
2021-03-30 15:04   ` [PATCH v4 15/16] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-03-30 15:04   ` [PATCH v4 16/16] midx.c: improve cache locality in midx_pack_order_cmp() Taylor Blau
2021-03-30 15:45   ` [PATCH v4 00/16] midx: implement a multi-pack reverse index Jeff King
2021-03-30 15:49     ` Taylor Blau
2021-03-30 16:01       ` Jeff King

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