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reftable: make the compaction factor configurable 

When auto-compacting, the reftable library packs references such that
the sizes of the tables form a geometric sequence. The factor for this
geometric sequence is hardcoded to 2 right now. We're about to expose
this as a config option though, so let's expose the factor via write
options.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Patrick Steinhardt 2024-05-13 10:18:38 +02:00 committed by Junio C Hamano
parent afbdbfae0b
commit f663d34306
5 changed files with 21 additions and 7 deletions
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1
reftable/constants.h
View File

@ -17,5 +17,6 @@ https://developers.google.com/open-source/licenses/bsd

#define MAX_RESTARTS ((1 << 16) - 1)
#define DEFAULT_BLOCK_SIZE 4096
#define DEFAULT_GEOMETRIC_FACTOR 2

#endif

6
reftable/reftable-writer.h
View File

@ -45,6 +45,12 @@ struct reftable_write_options {

/* boolean: Prevent auto-compaction of tables. */
unsigned disable_auto_compact : 1;

/*
* Geometric sequence factor used by auto-compaction to decide which
* tables to compact. Defaults to 2 if unset.
*/
uint8_t auto_compaction_factor;
};

/* reftable_block_stats holds statistics for a single block type */

14
reftable/stack.c
View File

@ -10,6 +10,7 @@ https://developers.google.com/open-source/licenses/bsd

#include "../write-or-die.h"
#include "system.h"
#include "constants.h"
#include "merged.h"
#include "reader.h"
#include "reftable-error.h"
@ -1212,12 +1213,16 @@ static int segment_size(struct segment *s)
return s->end - s->start;
}

struct segment suggest_compaction_segment(uint64_t *sizes, size_t n)
struct segment suggest_compaction_segment(uint64_t *sizes, size_t n,
uint8_t factor)
{
struct segment seg = { 0 };
uint64_t bytes;
size_t i;

if (!factor)
factor = DEFAULT_GEOMETRIC_FACTOR;

/*
* If there are no tables or only a single one then we don't have to
* compact anything. The sequence is geometric by definition already.
@ -1249,7 +1254,7 @@ struct segment suggest_compaction_segment(uint64_t *sizes, size_t n)
* 64, 32, 16, 8, 4, 3, 1
*/
for (i = n - 1; i > 0; i--) {
if (sizes[i - 1] < sizes[i] * 2) {
if (sizes[i - 1] < sizes[i] * factor) {
seg.end = i + 1;
bytes = sizes[i];
break;
@ -1275,7 +1280,7 @@ struct segment suggest_compaction_segment(uint64_t *sizes, size_t n)
uint64_t curr = bytes;
bytes += sizes[i - 1];

if (sizes[i - 1] < curr * 2) {
if (sizes[i - 1] < curr * factor) {
seg.start = i - 1;
seg.bytes = bytes;
}
@ -1301,7 +1306,8 @@ int reftable_stack_auto_compact(struct reftable_stack *st)
{
uint64_t *sizes = stack_table_sizes_for_compaction(st);
struct segment seg =
suggest_compaction_segment(sizes, st->merged->stack_len);
suggest_compaction_segment(sizes, st->merged->stack_len,
st->opts.auto_compaction_factor);
reftable_free(sizes);
if (segment_size(&seg) > 0)
return stack_compact_range_stats(st, seg.start, seg.end - 1,

3
reftable/stack.h
View File

@ -35,6 +35,7 @@ struct segment {
uint64_t bytes;
};

struct segment suggest_compaction_segment(uint64_t *sizes, size_t n);
struct segment suggest_compaction_segment(uint64_t *sizes, size_t n,
uint8_t factor);

#endif

4
reftable/stack_test.c
View File

@ -729,7 +729,7 @@ static void test_suggest_compaction_segment(void)
{
uint64_t sizes[] = { 512, 64, 17, 16, 9, 9, 9, 16, 2, 16 };
struct segment min =
suggest_compaction_segment(sizes, ARRAY_SIZE(sizes));
suggest_compaction_segment(sizes, ARRAY_SIZE(sizes), 2);
EXPECT(min.start == 1);
EXPECT(min.end == 10);
}
@ -738,7 +738,7 @@ static void test_suggest_compaction_segment_nothing(void)
{
uint64_t sizes[] = { 64, 32, 16, 8, 4, 2 };
struct segment result =
suggest_compaction_segment(sizes, ARRAY_SIZE(sizes));
suggest_compaction_segment(sizes, ARRAY_SIZE(sizes), 2);
EXPECT(result.start == result.end);
}