[PATCH v5 08/11] midx: implement midx_repack()
- From
Derrick Stolee <stolee@gmail.com>
- Date
- Apr 24, 2019, 15:14 UTC
- Message-ID
- <20190424151428.170316-9-dstolee@microsoft.com>
- In-Reply-To
- <20190424151428.170316-1-dstolee@microsoft.com>
To repack with a non-zero batch-size, first sort all pack-files by their modified time. Second, walk those pack-files from oldest to newest, compute their expected size, and add the packs to a list if they are smaller than the given batch-size. Stop when the total expected size is at least the batch size.
If the batch size is zero, select all packs in the multi-pack-index.
Finally, collect the objects from the multi-pack-index that are in the selected packs and send them to 'git pack-objects'. Write a new multi-pack-index that includes the new pack.
Using a batch size of zero is very similar to a standard 'git repack' command, except that we do not delete the old packs and instead rely on the new multi-pack-index to prevent new processes from reading the old packs. This does not disrupt other Git processes that are currently reading the old packs based on the old multi-pack-index.
While first designing a 'git multi-pack-index repack' operation, I started by collecting the batches based on the actual size of the objects instead of the size of the pack-files. This allows repacking a large pack-file that has very few referencd objects. However, this came at a significant cost of parsing pack-files instead of simply reading the multi-pack-index and getting the file information for the pack-files. The "expected size" version provides similar behavior, but could skip a pack-file if the average object size is much larger than the actual size of the referenced objects, or can create a large pack if the actual size of the referenced objects is larger than the expected size.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com> --- midx.c | 150 +++++++++++++++++++++++++++++++++++- t/t5319-multi-pack-index.sh | 28 +++++++ 2 files changed, 177 insertions(+), 1 deletion(-)
diff --git a/midx.c b/midx.c index 768a7dff73..01c6a05732 100644 --- a/midx.c +++ b/midx.c @@ -8,6 +8,7 @@ #include "sha1-lookup.h" #include "midx.h" #include "progress.h" +#include "run-command.h" #define MIDX_SIGNATURE 0x4d494458 /* "MIDX" */ #define MIDX_VERSION 1 @@ -1113,7 +1114,154 @@ int expire_midx_packs(const char *object_dir) return result; } -int midx_repack(const char *object_dir, size_t batch_size) +struct repack_info { + timestamp_t mtime; + uint32_t referenced_objects; + uint32_t pack_int_id; +}; + +static int compare_by_mtime(const void *a_, const void *b_) { + const struct repack_info *a, *b; + + a = (const struct repack_info *)a_; + b = (const struct repack_info *)b_; + + if (a->mtime < b->mtime) + return -1; + if (a->mtime > b->mtime) + return 1; + return 0; +} + +static int fill_included_packs_all(struct multi_pack_index *m, + unsigned char *include_pack) +{ + uint32_t i; + + for (i = 0; i < m->num_packs; i++) + include_pack[i] = 1; + + return m->num_packs < 2; +} + +static int fill_included_packs_batch(struct multi_pack_index *m, + unsigned char *include_pack, + size_t batch_size) +{ + uint32_t i, packs_to_repack; + size_t total_size; + struct repack_info *pack_info = xcalloc(m->num_packs, sizeof(struct repack_info)); + + for (i = 0; i < m->num_packs; i++) { + pack_info[i].pack_int_id = i; + + if (prepare_midx_pack(m, i)) + continue; + + pack_info[i].mtime = m->packs[i]->mtime; + } + + for (i = 0; batch_size && i < m->num_objects; i++) { + uint32_t pack_int_id = nth_midxed_pack_int_id(m, i); + pack_info[pack_int_id].referenced_objects++; + } + + QSORT(pack_info, m->num_packs, compare_by_mtime); + + total_size = 0; + packs_to_repack = 0; + for (i = 0; total_size < batch_size && i < m->num_packs; i++) { + int pack_int_id = pack_info[i].pack_int_id; + struct packed_git *p = m->packs[pack_int_id]; + size_t expected_size; + + if (!p) + continue; + if (open_pack_index(p) || !p->num_objects) + continue; + + expected_size = (size_t)(p->pack_size + * pack_info[i].referenced_objects); + expected_size /= p->num_objects; + + if (expected_size >= batch_size) + continue; + + packs_to_repack++; + total_size += expected_size; + include_pack[pack_int_id] = 1; + } + + free(pack_info); + + if (total_size < batch_size || packs_to_repack < 2) + return 1; + return 0; +} + +int midx_repack(const char *object_dir, size_t batch_size) +{ + int result = 0; + uint32_t i; + unsigned char *include_pack; + struct child_process cmd = CHILD_PROCESS_INIT; + struct strbuf base_name = STRBUF_INIT; + struct multi_pack_index *m = load_multi_pack_index(object_dir, 1); + + if (!m) + return 0; + + include_pack = xcalloc(m->num_packs, sizeof(unsigned char)); + + if (batch_size) { + if (fill_included_packs_batch(m, include_pack, batch_size)) + goto cleanup; + } else if (fill_included_packs_all(m, include_pack)) + goto cleanup; + + argv_array_push(&cmd.args, "pack-objects"); + + strbuf_addstr(&base_name, object_dir); + strbuf_addstr(&base_name, "/pack/pack"); + argv_array_push(&cmd.args, base_name.buf); + strbuf_release(&base_name); + + cmd.git_cmd = 1; + cmd.in = cmd.out = -1; + + if (start_command(&cmd)) { + error(_("could not start pack-objects")); + result = 1; + goto cleanup; + } + + for (i = 0; i < m->num_objects; i++) { + struct object_id oid; + uint32_t pack_int_id = nth_midxed_pack_int_id(m, i); + + if (!include_pack[pack_int_id]) + continue; + + nth_midxed_object_oid(&oid, m, i); + xwrite(cmd.in, oid_to_hex(&oid), the_hash_algo->hexsz); + xwrite(cmd.in, "\n", 1); + } + close(cmd.in); + + if (finish_command(&cmd)) { + error(_("could not finish pack-objects")); + result = 1; + goto cleanup; + } + + result = write_midx_internal(object_dir, m, NULL); + m = NULL; + +cleanup: + if (m) + close_midx(m); + free(include_pack); + return result; } diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh index 26ae8b3f62..d6c1353514 100755 --- a/t/t5319-multi-pack-index.sh +++ b/t/t5319-multi-pack-index.sh @@ -435,4 +435,32 @@ test_expect_success 'repack with minimum size does not alter existing packs' ' ) ' +test_expect_success 'repack creates a new pack' ' + ( + cd dup && + ls .git/objects/pack/*idx >idx-list && + test_line_count = 5 idx-list && + THIRD_SMALLEST_SIZE=$(ls -l .git/objects/pack/*pack | awk "{print \$5;}" | sort -n | head -n 3 | tail -n 1) && + BATCH_SIZE=$(($THIRD_SMALLEST_SIZE + 1)) && + git multi-pack-index repack --batch-size=$BATCH_SIZE && + ls .git/objects/pack/*idx >idx-list && + test_line_count = 6 idx-list && + test-tool read-midx .git/objects | grep idx >midx-list && + test_line_count = 6 midx-list + ) +' + +test_expect_success 'expire removes repacked packs' ' + ( + cd dup && + ls -al .git/objects/pack/*pack && + ls -S .git/objects/pack/*pack | head -n 4 >expect && + git multi-pack-index expire && + ls -S .git/objects/pack/*pack >actual && + test_cmp expect actual && + test-tool read-midx .git/objects | grep idx >midx-list && + test_line_count = 4 midx-list + ) +' + test_done
-- 2.21.0.1096.g1c91fdc207