From: "Justin Tobler via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Patrick Steinhardt <ps@pks.im>,
Karthik Nayak <karthik.188@gmail.com>,
Justin Tobler <jltobler@gmail.com>
Subject: [PATCH v3 0/3] reftable/stack: use geometric table compaction
Date: Fri, 29 Mar 2024 04:16:46 +0000 [thread overview]
Message-ID: <pull.1683.v3.git.1711685809.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.1683.v2.git.1711060819.gitgitgadget@gmail.com>
Hello again,
This is the third version my patch series that refactors the reftable
compaction strategy to instead follow a geometric sequence. Changes compared
to v2:
* Added test to validate the GIT_TEST_REFTABLE_NO_AUTOCOMPACTION
environment variable works as expected.
* Added additional clarifying comments and examples to explain how the new
compaction strategy works.
* Removed outdated comment from stack_test.c test
Thanks for taking a look!
-Justin
Justin Tobler (3):
reftable/stack: add env to disable autocompaction
reftable/stack: use geometric table compaction
reftable/stack: make segment end inclusive
reftable/stack.c | 124 ++++++++++++++++++-------------------
reftable/stack.h | 3 -
reftable/stack_test.c | 67 +++++---------------
reftable/system.h | 1 +
t/t0610-reftable-basics.sh | 58 ++++++++++++-----
5 files changed, 120 insertions(+), 133 deletions(-)
base-commit: c75fd8d8150afdf836b63a8e0534d9b9e3e111ba
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1683%2Fjltobler%2Fjt%2Freftable-geometric-compaction-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1683/jltobler/jt/reftable-geometric-compaction-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1683
Range-diff vs v2:
1: cb6b152e5c8 ! 1: 2fdd8ea1133 reftable/stack: add env to disable autocompaction
@@ reftable/stack.c: int reftable_addition_commit(struct reftable_addition *add)
## reftable/system.h ##
@@ reftable/system.h: license that can be found in the LICENSE file or at
- #include "strbuf.h"
+ #include "tempfile.h"
#include "hash-ll.h" /* hash ID, sizes.*/
#include "dir.h" /* remove_dir_recursively, for tests.*/
+#include "parse.h"
int hash_size(uint32_t id);
+
+ ## t/t0610-reftable-basics.sh ##
+@@ t/t0610-reftable-basics.sh: test_expect_success 'ref transaction: writes cause auto-compaction' '
+ test_line_count = 1 repo/.git/reftable/tables.list
+ '
+
++test_expect_success 'ref transaction: environment variable disables auto-compaction' '
++ test_when_finished "rm -rf repo" &&
++
++ git init repo &&
++ test_commit -C repo A &&
++ for i in $(test_seq 20)
++ do
++ GIT_TEST_REFTABLE_NO_AUTOCOMPACTION=true git -C repo update-ref branch-$i HEAD || return 1
++ done &&
++ test_line_count = 23 repo/.git/reftable/tables.list &&
++
++ git -C repo update-ref foo HEAD &&
++ test_line_count = 1 repo/.git/reftable/tables.list
++'
++
+ check_fsync_events () {
+ local trace="$1" &&
+ shift &&
2: def70084523 ! 2: 7e62c2286ae reftable/stack: use geometric table compaction
@@ Commit message
Instead, to avoid unbounded growth of the table list, the compaction
strategy is updated to ensure tables follow a geometric sequence after
- each operation. This is done by walking the table list in reverse index
- order to identify the compaction segment start and end. The compaction
- segment end is found by identifying the first table which has a
- preceding table size less than twice the current table. Next, the
- compaction segment start is found iterating through the remaining tables
- in the list checking if the previous table size is less than twice the
- cumulative of tables from the segment end. This ensures the correct
- segment start is found and that the newly compacted table does not
- violate the geometric sequence.
+ each operation by individually evaluating each table in reverse index
+ order. This strategy results in a much simpler and more robust algorithm
+ compared to the previous one while also maintaining a minimal ordered
+ set of tables on-disk.
When creating 10 thousand references, the new strategy has no
performance impact:
@@ reftable/stack.c: static int segment_size(struct segment *s)
+ * they are already valid members of the geometric sequence. Due to the
+ * properties of a geometric sequence, it is not possible for the sum of
+ * these tables to exceed the value of the ending point table.
++ *
++ * Example table size sequence requiring no compaction:
++ * 64, 32, 16, 8, 4, 2, 1
++ *
++ * Example compaction segment end set to table with size 3:
++ * 64, 32, 16, 8, 4, 3, 1
+ */
+ for (i = n - 1; i > 0; i--) {
+ if (sizes[i - 1] < sizes[i] * 2) {
@@ reftable/stack.c: static int segment_size(struct segment *s)
break;
+ }
+ }
-+
+
+- min_seg.start = prev;
+- min_seg.bytes += sizes[prev];
+ /*
+ * Find the starting table of the compaction segment by iterating
+ * through the remaining tables and keeping track of the accumulated
-+ * size of all tables seen from the segment end table.
++ * size of all tables seen from the segment end table. The previous
++ * table is compared to the accumulated size because the tables from the
++ * segment end are merged backwards recursively.
+ *
+ * Note that we keep iterating even after we have found the first
+ * starting point. This is because there may be tables in the stack
+ * preceding that first starting point which violate the geometric
+ * sequence.
++ *
++ * Example compaction segment start set to table with size 32:
++ * 128, 32, 16, 8, 4, 3, 1
+ */
+ for (; i > 0; i--) {
+ uint64_t curr = bytes;
+ bytes += sizes[i - 1];
-
-- min_seg.start = prev;
-- min_seg.bytes += sizes[prev];
++
+ if (sizes[i - 1] < curr * 2) {
+ seg.start = i - 1;
+ seg.bytes = bytes;
@@ reftable/stack_test.c: static void test_reftable_stack_hash_id(void)
static void test_suggest_compaction_segment(void)
{
- uint64_t sizes[] = { 128, 64, 17, 16, 9, 9, 9, 16, 16 };
+- /* .................0 1 2 3 4 5 6 */
+ uint64_t sizes[] = { 512, 64, 17, 16, 9, 9, 9, 16, 2, 16 };
- /* .................0 1 2 3 4 5 6 */
struct segment min =
suggest_compaction_segment(sizes, ARRAY_SIZE(sizes));
- EXPECT(min.start == 2);
@@ t/t0610-reftable-basics.sh: test_expect_success 'ref transaction: writes cause a
test_commit -C repo --no-tag B &&
test_line_count = 1 repo/.git/reftable/tables.list
+@@ t/t0610-reftable-basics.sh: test_expect_success 'ref transaction: environment variable disables auto-compact
+ do
+ GIT_TEST_REFTABLE_NO_AUTOCOMPACTION=true git -C repo update-ref branch-$i HEAD || return 1
+ done &&
+- test_line_count = 23 repo/.git/reftable/tables.list &&
++ test_line_count = 22 repo/.git/reftable/tables.list &&
+
+ git -C repo update-ref foo HEAD &&
+ test_line_count = 1 repo/.git/reftable/tables.list
'
+test_expect_success 'ref transaction: alternating table sizes are compacted' '
3: a23e3fc6972 ! 3: 9a33914c852 reftable/segment: make segment end inclusive
@@ Metadata
Author: Justin Tobler <jltobler@gmail.com>
## Commit message ##
- reftable/segment: make segment end inclusive
+ reftable/stack: make segment end inclusive
For a reftable segment, the start of the range is inclusive and the end
is exclusive. In practice we increment the end when creating the
--
gitgitgadget
next prev parent reply other threads:[~2024-03-29 4:16 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-05 20:03 [PATCH] reftable/stack: use geometric table compaction Justin Tobler via GitGitGadget
2024-03-06 12:30 ` Patrick Steinhardt
2024-03-06 12:37 ` Patrick Steinhardt
2024-03-21 22:48 ` Justin Tobler
2024-03-21 22:40 ` [PATCH v2 0/3] " Justin Tobler via GitGitGadget
2024-03-21 22:40 ` [PATCH v2 1/3] reftable/stack: add env to disable autocompaction Justin Tobler via GitGitGadget
2024-03-22 1:25 ` Patrick Steinhardt
2024-03-21 22:40 ` [PATCH v2 2/3] reftable/stack: use geometric table compaction Justin Tobler via GitGitGadget
2024-03-22 1:25 ` Patrick Steinhardt
2024-03-27 13:24 ` Karthik Nayak
2024-03-21 22:40 ` [PATCH v2 3/3] reftable/segment: make segment end inclusive Justin Tobler via GitGitGadget
2024-03-22 1:25 ` [PATCH v2 0/3] reftable/stack: use geometric table compaction Patrick Steinhardt
2024-04-03 10:13 ` Han-Wen Nienhuys
2024-04-03 10:18 ` Patrick Steinhardt
2024-04-03 15:14 ` Justin Tobler
2024-04-03 16:40 ` Junio C Hamano
2024-03-29 4:16 ` Justin Tobler via GitGitGadget [this message]
2024-03-29 4:16 ` [PATCH v3 1/3] reftable/stack: add env to disable autocompaction Justin Tobler via GitGitGadget
2024-03-29 18:25 ` Junio C Hamano
2024-03-29 21:56 ` Junio C Hamano
2024-04-02 7:23 ` Patrick Steinhardt
2024-04-02 17:23 ` Junio C Hamano
2024-03-29 4:16 ` [PATCH v3 2/3] reftable/stack: use geometric table compaction Justin Tobler via GitGitGadget
2024-04-02 7:23 ` Patrick Steinhardt
2024-03-29 4:16 ` [PATCH v3 3/3] reftable/stack: make segment end inclusive Justin Tobler via GitGitGadget
2024-03-29 18:36 ` Junio C Hamano
2024-04-02 7:23 ` Patrick Steinhardt
2024-04-03 0:20 ` [PATCH v4 0/2] reftable/stack: use geometric table compaction Justin Tobler via GitGitGadget
2024-04-03 0:20 ` [PATCH v4 1/2] reftable/stack: add env to disable autocompaction Justin Tobler via GitGitGadget
2024-04-03 0:20 ` [PATCH v4 2/2] reftable/stack: use geometric table compaction Justin Tobler via GitGitGadget
2024-04-03 4:47 ` [PATCH v4 0/2] " Patrick Steinhardt
2024-04-03 11:12 ` Karthik Nayak
2024-04-03 16:56 ` Junio C Hamano
2024-04-04 18:29 ` [PATCH v5 0/3] " Justin Tobler via GitGitGadget
2024-04-04 18:29 ` [PATCH v5 1/3] reftable/stack: allow disabling of auto-compaction Justin Tobler via GitGitGadget
2024-04-08 6:12 ` Patrick Steinhardt
2024-04-04 18:29 ` [PATCH v5 2/3] reftable/stack: add env to disable autocompaction Justin Tobler via GitGitGadget
2024-04-08 6:12 ` Patrick Steinhardt
2024-04-08 16:18 ` Junio C Hamano
2024-04-04 18:29 ` [PATCH v5 3/3] reftable/stack: use geometric table compaction Justin Tobler via GitGitGadget
2024-04-08 6:12 ` [PATCH v5 0/3] " Patrick Steinhardt
2024-04-08 16:17 ` Justin Tobler
2024-04-08 16:16 ` [PATCH v6 " Justin Tobler via GitGitGadget
2024-04-08 16:16 ` [PATCH v6 1/3] reftable/stack: expose option to disable auto-compaction Justin Tobler via GitGitGadget
2024-04-08 16:16 ` [PATCH v6 2/3] reftable/stack: add env to disable autocompaction Justin Tobler via GitGitGadget
2024-04-08 16:16 ` [PATCH v6 3/3] reftable/stack: use geometric table compaction Justin Tobler via GitGitGadget
2024-04-08 16:20 ` [PATCH v6 0/3] " Patrick Steinhardt
2024-04-08 19:12 ` Junio C Hamano
2024-04-03 19:12 ` [PATCH v2 " Junio C Hamano
2024-04-03 19:30 ` Patrick Steinhardt
2024-04-04 5:34 ` Patrick Steinhardt
2024-04-04 18:28 ` Justin Tobler
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