Files
git/t/unit-tests/t-reftable-block.c
Patrick Steinhardt 1970333644 reftable: fix perf regression when reading blocks of unwanted type
In fd888311fb (reftable/table: move reading block into block reader,
2025-04-07), we have refactored how reftable blocks are read so that
most of the logic is contained in the "block.c" subsystem itself. Most
importantly, the whole logic to read the data itself is now contained in
that subsystem.

This change caused a significant performance regression though when
reading blocks that aren't of the specific type one is searching for:

    Benchmark 1: update-ref: create 100k refs (revision = fd888311fbc~)
      Time (mean ± σ):      2.171 s ±  0.028 s    [User: 1.189 s, System: 0.977 s]
      Range (min … max):    2.117 s …  2.206 s    10 runs

    Benchmark 2: update-ref: create 100k refs (revision = fd888311fb)
      Time (mean ± σ):      3.418 s ±  0.030 s    [User: 2.371 s, System: 1.037 s]
      Range (min … max):    3.377 s …  3.473 s    10 runs

    Summary
      update-ref: create 100k refs (revision = fd888311fbc~) ran
        1.57 ± 0.02 times faster than update-ref: create 100k refs (revision = fd888311fb)

The root caute of the performance regression is that we changed when
exactly blocks of an uninteresting type are being discarded. Previous to
the refactoring in the mentioned commit we'd load the block data, read
its type, notice that it's not the wanted type and discard the block.
After the commit though we don't discard the block immediately, but we
fully decode it only to realize that it's not the desired type. We then
discard the block again, but have already performed a bunch of pointless
work.

Fix the regression by making `reftable_block_init()` return early in
case the block is not of the desired type. This fixes the performance
hit:

    Benchmark 1: update-ref: create 100k refs (revision = HEAD~)
      Time (mean ± σ):      2.712 s ±  0.018 s    [User: 1.990 s, System: 0.716 s]
      Range (min … max):    2.682 s …  2.741 s    10 runs

    Benchmark 2: update-ref: create 100k refs (revision = HEAD)
      Time (mean ± σ):      1.670 s ±  0.012 s    [User: 0.991 s, System: 0.676 s]
      Range (min … max):    1.652 s …  1.693 s    10 runs

    Summary
      update-ref: create 100k refs (revision = HEAD) ran
        1.62 ± 0.02 times faster than update-ref: create 100k refs (revision = HEAD~)

Note that the baseline performance is lower than in the original due to
a couple of unrelated performance improvements that have landed since
the original commit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2025-05-12 10:55:24 -07:00

467 lines
12 KiB
C

/*
Copyright 2020 Google LLC
Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file or at
https://developers.google.com/open-source/licenses/bsd
*/
#include "test-lib.h"
#include "reftable/block.h"
#include "reftable/blocksource.h"
#include "reftable/constants.h"
#include "reftable/reftable-error.h"
#include "strbuf.h"
static void t_ref_block_read_write(void)
{
const int header_off = 21; /* random */
struct reftable_record recs[30];
const size_t N = ARRAY_SIZE(recs);
const size_t block_size = 1024;
struct reftable_block_source source = { 0 };
struct block_writer bw = {
.last_key = REFTABLE_BUF_INIT,
};
struct reftable_record rec = {
.type = REFTABLE_BLOCK_TYPE_REF,
};
size_t i = 0;
int ret;
struct reftable_block block = { 0 };
struct block_iter it = BLOCK_ITER_INIT;
struct reftable_buf want = REFTABLE_BUF_INIT;
struct reftable_buf block_data = REFTABLE_BUF_INIT;
REFTABLE_CALLOC_ARRAY(block_data.buf, block_size);
check(block_data.buf != NULL);
block_data.len = block_size;
ret = block_writer_init(&bw, REFTABLE_BLOCK_TYPE_REF, (uint8_t *) block_data.buf, block_size,
header_off, hash_size(REFTABLE_HASH_SHA1));
check(!ret);
rec.u.ref.refname = (char *) "";
rec.u.ref.value_type = REFTABLE_REF_DELETION;
ret = block_writer_add(&bw, &rec);
check_int(ret, ==, REFTABLE_API_ERROR);
for (i = 0; i < N; i++) {
rec.u.ref.refname = xstrfmt("branch%02"PRIuMAX, (uintmax_t)i);
rec.u.ref.value_type = REFTABLE_REF_VAL1;
memset(rec.u.ref.value.val1, i, REFTABLE_HASH_SIZE_SHA1);
recs[i] = rec;
ret = block_writer_add(&bw, &rec);
rec.u.ref.refname = NULL;
rec.u.ref.value_type = REFTABLE_REF_DELETION;
check_int(ret, ==, 0);
}
ret = block_writer_finish(&bw);
check_int(ret, >, 0);
block_writer_release(&bw);
block_source_from_buf(&source ,&block_data);
reftable_block_init(&block, &source, 0, header_off, block_size,
REFTABLE_HASH_SIZE_SHA1, REFTABLE_BLOCK_TYPE_REF);
block_iter_init(&it, &block);
for (i = 0; ; i++) {
ret = block_iter_next(&it, &rec);
check_int(ret, >=, 0);
if (ret > 0) {
check_int(i, ==, N);
break;
}
check(reftable_record_equal(&recs[i], &rec, REFTABLE_HASH_SIZE_SHA1));
}
for (i = 0; i < N; i++) {
reftable_record_key(&recs[i], &want);
ret = block_iter_seek_key(&it, &want);
check_int(ret, ==, 0);
ret = block_iter_next(&it, &rec);
check_int(ret, ==, 0);
check(reftable_record_equal(&recs[i], &rec, REFTABLE_HASH_SIZE_SHA1));
want.len--;
ret = block_iter_seek_key(&it, &want);
check_int(ret, ==, 0);
ret = block_iter_next(&it, &rec);
check_int(ret, ==, 0);
check(reftable_record_equal(&recs[10 * (i / 10)], &rec, REFTABLE_HASH_SIZE_SHA1));
}
reftable_block_release(&block);
block_iter_close(&it);
reftable_record_release(&rec);
reftable_buf_release(&want);
reftable_buf_release(&block_data);
for (i = 0; i < N; i++)
reftable_record_release(&recs[i]);
}
static void t_log_block_read_write(void)
{
const int header_off = 21;
struct reftable_record recs[30];
const size_t N = ARRAY_SIZE(recs);
const size_t block_size = 2048;
struct reftable_block_source source = { 0 };
struct block_writer bw = {
.last_key = REFTABLE_BUF_INIT,
};
struct reftable_record rec = {
.type = REFTABLE_BLOCK_TYPE_LOG,
};
size_t i = 0;
int ret;
struct reftable_block block = { 0 };
struct block_iter it = BLOCK_ITER_INIT;
struct reftable_buf want = REFTABLE_BUF_INIT;
struct reftable_buf block_data = REFTABLE_BUF_INIT;
REFTABLE_CALLOC_ARRAY(block_data.buf, block_size);
check(block_data.buf != NULL);
block_data.len = block_size;
ret = block_writer_init(&bw, REFTABLE_BLOCK_TYPE_LOG, (uint8_t *) block_data.buf, block_size,
header_off, hash_size(REFTABLE_HASH_SHA1));
check(!ret);
for (i = 0; i < N; i++) {
rec.u.log.refname = xstrfmt("branch%02"PRIuMAX , (uintmax_t)i);
rec.u.log.update_index = i;
rec.u.log.value_type = REFTABLE_LOG_UPDATE;
recs[i] = rec;
ret = block_writer_add(&bw, &rec);
rec.u.log.refname = NULL;
rec.u.log.value_type = REFTABLE_LOG_DELETION;
check_int(ret, ==, 0);
}
ret = block_writer_finish(&bw);
check_int(ret, >, 0);
block_writer_release(&bw);
block_source_from_buf(&source, &block_data);
reftable_block_init(&block, &source, 0, header_off, block_size,
REFTABLE_HASH_SIZE_SHA1, REFTABLE_BLOCK_TYPE_LOG);
block_iter_init(&it, &block);
for (i = 0; ; i++) {
ret = block_iter_next(&it, &rec);
check_int(ret, >=, 0);
if (ret > 0) {
check_int(i, ==, N);
break;
}
check(reftable_record_equal(&recs[i], &rec, REFTABLE_HASH_SIZE_SHA1));
}
for (i = 0; i < N; i++) {
reftable_buf_reset(&want);
check(!reftable_buf_addstr(&want, recs[i].u.log.refname));
ret = block_iter_seek_key(&it, &want);
check_int(ret, ==, 0);
ret = block_iter_next(&it, &rec);
check_int(ret, ==, 0);
check(reftable_record_equal(&recs[i], &rec, REFTABLE_HASH_SIZE_SHA1));
want.len--;
ret = block_iter_seek_key(&it, &want);
check_int(ret, ==, 0);
ret = block_iter_next(&it, &rec);
check_int(ret, ==, 0);
check(reftable_record_equal(&recs[10 * (i / 10)], &rec, REFTABLE_HASH_SIZE_SHA1));
}
reftable_block_release(&block);
block_iter_close(&it);
reftable_record_release(&rec);
reftable_buf_release(&want);
reftable_buf_release(&block_data);
for (i = 0; i < N; i++)
reftable_record_release(&recs[i]);
}
static void t_obj_block_read_write(void)
{
const int header_off = 21;
struct reftable_record recs[30];
const size_t N = ARRAY_SIZE(recs);
const size_t block_size = 1024;
struct reftable_block_source source = { 0 };
struct block_writer bw = {
.last_key = REFTABLE_BUF_INIT,
};
struct reftable_record rec = {
.type = REFTABLE_BLOCK_TYPE_OBJ,
};
size_t i = 0;
int ret;
struct reftable_block block = { 0 };
struct block_iter it = BLOCK_ITER_INIT;
struct reftable_buf want = REFTABLE_BUF_INIT;
struct reftable_buf block_data = REFTABLE_BUF_INIT;
REFTABLE_CALLOC_ARRAY(block_data.buf, block_size);
check(block_data.buf != NULL);
block_data.len = block_size;
ret = block_writer_init(&bw, REFTABLE_BLOCK_TYPE_OBJ, (uint8_t *) block_data.buf, block_size,
header_off, hash_size(REFTABLE_HASH_SHA1));
check(!ret);
for (i = 0; i < N; i++) {
uint8_t bytes[] = { i, i + 1, i + 2, i + 3, i + 5 }, *allocated;
DUP_ARRAY(allocated, bytes, ARRAY_SIZE(bytes));
rec.u.obj.hash_prefix = allocated;
rec.u.obj.hash_prefix_len = 5;
recs[i] = rec;
ret = block_writer_add(&bw, &rec);
rec.u.obj.hash_prefix = NULL;
rec.u.obj.hash_prefix_len = 0;
check_int(ret, ==, 0);
}
ret = block_writer_finish(&bw);
check_int(ret, >, 0);
block_writer_release(&bw);
block_source_from_buf(&source, &block_data);
reftable_block_init(&block, &source, 0, header_off, block_size,
REFTABLE_HASH_SIZE_SHA1, REFTABLE_BLOCK_TYPE_OBJ);
block_iter_init(&it, &block);
for (i = 0; ; i++) {
ret = block_iter_next(&it, &rec);
check_int(ret, >=, 0);
if (ret > 0) {
check_int(i, ==, N);
break;
}
check(reftable_record_equal(&recs[i], &rec, REFTABLE_HASH_SIZE_SHA1));
}
for (i = 0; i < N; i++) {
reftable_record_key(&recs[i], &want);
ret = block_iter_seek_key(&it, &want);
check_int(ret, ==, 0);
ret = block_iter_next(&it, &rec);
check_int(ret, ==, 0);
check(reftable_record_equal(&recs[i], &rec, REFTABLE_HASH_SIZE_SHA1));
}
reftable_block_release(&block);
block_iter_close(&it);
reftable_record_release(&rec);
reftable_buf_release(&want);
reftable_buf_release(&block_data);
for (i = 0; i < N; i++)
reftable_record_release(&recs[i]);
}
static void t_index_block_read_write(void)
{
const int header_off = 21;
struct reftable_record recs[30];
const size_t N = ARRAY_SIZE(recs);
const size_t block_size = 1024;
struct reftable_block_source source = { 0 };
struct block_writer bw = {
.last_key = REFTABLE_BUF_INIT,
};
struct reftable_record rec = {
.type = REFTABLE_BLOCK_TYPE_INDEX,
.u.idx.last_key = REFTABLE_BUF_INIT,
};
size_t i = 0;
int ret;
struct reftable_block block = { 0 };
struct block_iter it = BLOCK_ITER_INIT;
struct reftable_buf want = REFTABLE_BUF_INIT;
struct reftable_buf block_data = REFTABLE_BUF_INIT;
REFTABLE_CALLOC_ARRAY(block_data.buf, block_size);
check(block_data.buf != NULL);
block_data.len = block_size;
ret = block_writer_init(&bw, REFTABLE_BLOCK_TYPE_INDEX, (uint8_t *) block_data.buf, block_size,
header_off, hash_size(REFTABLE_HASH_SHA1));
check(!ret);
for (i = 0; i < N; i++) {
char buf[128];
snprintf(buf, sizeof(buf), "branch%02"PRIuMAX, (uintmax_t)i);
reftable_buf_init(&recs[i].u.idx.last_key);
recs[i].type = REFTABLE_BLOCK_TYPE_INDEX;
check(!reftable_buf_addstr(&recs[i].u.idx.last_key, buf));
recs[i].u.idx.offset = i;
ret = block_writer_add(&bw, &recs[i]);
check_int(ret, ==, 0);
}
ret = block_writer_finish(&bw);
check_int(ret, >, 0);
block_writer_release(&bw);
block_source_from_buf(&source, &block_data);
reftable_block_init(&block, &source, 0, header_off, block_size,
REFTABLE_HASH_SIZE_SHA1, REFTABLE_BLOCK_TYPE_INDEX);
block_iter_init(&it, &block);
for (i = 0; ; i++) {
ret = block_iter_next(&it, &rec);
check_int(ret, >=, 0);
if (ret > 0) {
check_int(i, ==, N);
break;
}
check(reftable_record_equal(&recs[i], &rec, REFTABLE_HASH_SIZE_SHA1));
}
for (i = 0; i < N; i++) {
reftable_record_key(&recs[i], &want);
ret = block_iter_seek_key(&it, &want);
check_int(ret, ==, 0);
ret = block_iter_next(&it, &rec);
check_int(ret, ==, 0);
check(reftable_record_equal(&recs[i], &rec, REFTABLE_HASH_SIZE_SHA1));
want.len--;
ret = block_iter_seek_key(&it, &want);
check_int(ret, ==, 0);
ret = block_iter_next(&it, &rec);
check_int(ret, ==, 0);
check(reftable_record_equal(&recs[10 * (i / 10)], &rec, REFTABLE_HASH_SIZE_SHA1));
}
reftable_block_release(&block);
block_iter_close(&it);
reftable_record_release(&rec);
reftable_buf_release(&want);
reftable_buf_release(&block_data);
for (i = 0; i < N; i++)
reftable_record_release(&recs[i]);
}
static void t_block_iterator(void)
{
struct reftable_block_source source = { 0 };
struct block_writer writer = {
.last_key = REFTABLE_BUF_INIT,
};
struct reftable_record expected_refs[20];
struct reftable_ref_record ref = { 0 };
struct reftable_iterator it = { 0 };
struct reftable_block block = { 0 };
struct reftable_buf data;
int err;
data.len = 1024;
REFTABLE_CALLOC_ARRAY(data.buf, data.len);
check(data.buf != NULL);
err = block_writer_init(&writer, REFTABLE_BLOCK_TYPE_REF, (uint8_t *) data.buf, data.len,
0, hash_size(REFTABLE_HASH_SHA1));
check(!err);
for (size_t i = 0; i < ARRAY_SIZE(expected_refs); i++) {
expected_refs[i] = (struct reftable_record) {
.type = REFTABLE_BLOCK_TYPE_REF,
.u.ref = {
.value_type = REFTABLE_REF_VAL1,
.refname = xstrfmt("refs/heads/branch-%02"PRIuMAX, (uintmax_t)i),
},
};
memset(expected_refs[i].u.ref.value.val1, i, REFTABLE_HASH_SIZE_SHA1);
err = block_writer_add(&writer, &expected_refs[i]);
check_int(err, ==, 0);
}
err = block_writer_finish(&writer);
check_int(err, >, 0);
block_source_from_buf(&source, &data);
reftable_block_init(&block, &source, 0, 0, data.len,
REFTABLE_HASH_SIZE_SHA1, REFTABLE_BLOCK_TYPE_REF);
err = reftable_block_init_iterator(&block, &it);
check_int(err, ==, 0);
for (size_t i = 0; ; i++) {
err = reftable_iterator_next_ref(&it, &ref);
if (err > 0) {
check_int(i, ==, ARRAY_SIZE(expected_refs));
break;
}
check_int(err, ==, 0);
check(reftable_ref_record_equal(&ref, &expected_refs[i].u.ref,
REFTABLE_HASH_SIZE_SHA1));
}
err = reftable_iterator_seek_ref(&it, "refs/heads/does-not-exist");
check_int(err, ==, 0);
err = reftable_iterator_next_ref(&it, &ref);
check_int(err, ==, 1);
err = reftable_iterator_seek_ref(&it, "refs/heads/branch-13");
check_int(err, ==, 0);
err = reftable_iterator_next_ref(&it, &ref);
check_int(err, ==, 0);
check(reftable_ref_record_equal(&ref, &expected_refs[13].u.ref,
REFTABLE_HASH_SIZE_SHA1));
for (size_t i = 0; i < ARRAY_SIZE(expected_refs); i++)
reftable_free(expected_refs[i].u.ref.refname);
reftable_ref_record_release(&ref);
reftable_iterator_destroy(&it);
reftable_block_release(&block);
block_writer_release(&writer);
reftable_buf_release(&data);
}
int cmd_main(int argc UNUSED, const char *argv[] UNUSED)
{
TEST(t_index_block_read_write(), "read-write operations on index blocks work");
TEST(t_log_block_read_write(), "read-write operations on log blocks work");
TEST(t_obj_block_read_write(), "read-write operations on obj blocks work");
TEST(t_ref_block_read_write(), "read-write operations on ref blocks work");
TEST(t_block_iterator(), "block iterator works");
return test_done();
}