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>
Patrick Steinhardt committed
May 13, 2024 at 10:18 UTC
f663d34306d414bca27cf6b5dc7affb00e8603fe
5 files changed
+21
-7
reftable/constants.h
+1
@@ -17,5 +17,6 @@ https://developers.google.com/open-source/licenses/bsd
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#define MAX_RESTARTS ((1 << 16) - 1)
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#define DEFAULT_BLOCK_SIZE 4096
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+#define DEFAULT_GEOMETRIC_FACTOR 2
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#endif
reftable/reftable-writer.h
+6
@@ -45,6 +45,12 @@ struct reftable_write_options {
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/* boolean: Prevent auto-compaction of tables. */
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unsigned disable_auto_compact : 1;
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+
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+ /*
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+ * Geometric sequence factor used by auto-compaction to decide which
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+ * tables to compact. Defaults to 2 if unset.
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+ */
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+ uint8_t auto_compaction_factor;
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};
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/* reftable_block_stats holds statistics for a single block type */
reftable/stack.c
+10
-4
@@ -10,6 +10,7 @@ https://developers.google.com/open-source/licenses/bsd
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#include "../write-or-die.h"
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#include "system.h"
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+#include "constants.h"
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#include "merged.h"
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#include "reader.h"
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#include "reftable-error.h"
@@ -1212,12 +1213,16 @@ static int segment_size(struct segment *s)
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return s->end - s->start;
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}
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-struct segment suggest_compaction_segment(uint64_t *sizes, size_t n)
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+struct segment suggest_compaction_segment(uint64_t *sizes, size_t n,
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+ uint8_t factor)
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{
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struct segment seg = { 0 };
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uint64_t bytes;
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size_t i;
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+ if (!factor)
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+ factor = DEFAULT_GEOMETRIC_FACTOR;
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+
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/*
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* If there are no tables or only a single one then we don't have to
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* compact anything. The sequence is geometric by definition already.
@@ -1249,7 +1254,7 @@ struct segment suggest_compaction_segment(uint64_t *sizes, size_t n)
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* 64, 32, 16, 8, 4, 3, 1
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*/
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for (i = n - 1; i > 0; i--) {
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- if (sizes[i - 1] < sizes[i] * 2) {
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+ if (sizes[i - 1] < sizes[i] * factor) {
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seg.end = i + 1;
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bytes = sizes[i];
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break;
@@ -1275,7 +1280,7 @@ struct segment suggest_compaction_segment(uint64_t *sizes, size_t n)
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uint64_t curr = bytes;
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bytes += sizes[i - 1];
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- if (sizes[i - 1] < curr * 2) {
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+ if (sizes[i - 1] < curr * factor) {
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seg.start = i - 1;
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seg.bytes = bytes;
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}
@@ -1301,7 +1306,8 @@ int reftable_stack_auto_compact(struct reftable_stack *st)
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{
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uint64_t *sizes = stack_table_sizes_for_compaction(st);
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struct segment seg =
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- suggest_compaction_segment(sizes, st->merged->stack_len);
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+ suggest_compaction_segment(sizes, st->merged->stack_len,
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+ st->opts.auto_compaction_factor);
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reftable_free(sizes);
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if (segment_size(&seg) > 0)
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return stack_compact_range_stats(st, seg.start, seg.end - 1,
reftable/stack.h
+2
-1
@@ -35,6 +35,7 @@ struct segment {
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uint64_t bytes;
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};
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-struct segment suggest_compaction_segment(uint64_t *sizes, size_t n);
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+struct segment suggest_compaction_segment(uint64_t *sizes, size_t n,
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+ uint8_t factor);
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#endif
reftable/stack_test.c
+2
-2
@@ -729,7 +729,7 @@ static void test_suggest_compaction_segment(void)
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{
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uint64_t sizes[] = { 512, 64, 17, 16, 9, 9, 9, 16, 2, 16 };
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struct segment min =
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- suggest_compaction_segment(sizes, ARRAY_SIZE(sizes));
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+ suggest_compaction_segment(sizes, ARRAY_SIZE(sizes), 2);
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EXPECT(min.start == 1);
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EXPECT(min.end == 10);
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}
@@ -738,7 +738,7 @@ static void test_suggest_compaction_segment_nothing(void)
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{
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uint64_t sizes[] = { 64, 32, 16, 8, 4, 2 };
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struct segment result =
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- suggest_compaction_segment(sizes, ARRAY_SIZE(sizes));
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+ suggest_compaction_segment(sizes, ARRAY_SIZE(sizes), 2);
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EXPECT(result.start == result.end);
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}
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