From ce1f213cc91cf545736048f28117fe1de89b8134 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Mon, 8 Apr 2024 14:17:04 +0200 Subject: reftable/block: reuse `zstream` state on inflation When calling `inflateInit()` and `inflate()`, the zlib library will allocate several data structures for the underlying `zstream` to keep track of various information. Thus, when inflating repeatedly, it is possible to optimize memory allocation patterns by reusing the `zstream` and then calling `inflateReset()` on it to prepare it for the next chunk of data to inflate. This is exactly what the reftable code is doing: when iterating through reflogs we need to potentially inflate many log blocks, but we discard the `zstream` every single time. Instead, as we reuse the `block_reader` for each of the blocks anyway, we can initialize the `zstream` once and then reuse it for subsequent inflations. Refactor the code to do so, which leads to a significant reduction in the number of allocations. The following measurements were done when iterating through 1 million reflog entries. Before: HEAP SUMMARY: in use at exit: 13,473 bytes in 122 blocks total heap usage: 23,028 allocs, 22,906 frees, 162,813,552 bytes allocated After: HEAP SUMMARY: in use at exit: 13,473 bytes in 122 blocks total heap usage: 302 allocs, 180 frees, 88,352 bytes allocated Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- reftable/block.c | 25 +++++++++++++++---------- reftable/block.h | 3 +++ reftable/reader.c | 1 + 3 files changed, 19 insertions(+), 10 deletions(-) diff --git a/reftable/block.c b/reftable/block.c index 435922b569..c6c4a68ea1 100644 --- a/reftable/block.c +++ b/reftable/block.c @@ -198,7 +198,6 @@ int block_reader_init(struct block_reader *br, struct reftable_block *block, uint32_t block_header_skip = 4 + header_off; uLong dst_len = sz - block_header_skip; uLong src_len = block->len - block_header_skip; - z_stream stream = {0}; /* Log blocks specify the *uncompressed* size in their header. */ REFTABLE_ALLOC_GROW(br->uncompressed_data, sz, @@ -207,16 +206,21 @@ int block_reader_init(struct block_reader *br, struct reftable_block *block, /* Copy over the block header verbatim. It's not compressed. */ memcpy(br->uncompressed_data, block->data, block_header_skip); - err = inflateInit(&stream); + if (!br->zstream) { + REFTABLE_CALLOC_ARRAY(br->zstream, 1); + err = inflateInit(br->zstream); + } else { + err = inflateReset(br->zstream); + } if (err != Z_OK) { err = REFTABLE_ZLIB_ERROR; goto done; } - stream.next_in = block->data + block_header_skip; - stream.avail_in = src_len; - stream.next_out = br->uncompressed_data + block_header_skip; - stream.avail_out = dst_len; + br->zstream->next_in = block->data + block_header_skip; + br->zstream->avail_in = src_len; + br->zstream->next_out = br->uncompressed_data + block_header_skip; + br->zstream->avail_out = dst_len; /* * We know both input as well as output size, and we know that @@ -225,15 +229,14 @@ int block_reader_init(struct block_reader *br, struct reftable_block *block, * here to instruct zlib to inflate the data in one go, which * is more efficient than using `Z_NO_FLUSH`. */ - err = inflate(&stream, Z_FINISH); - inflateEnd(&stream); + err = inflate(br->zstream, Z_FINISH); if (err != Z_STREAM_END) { err = REFTABLE_ZLIB_ERROR; goto done; } err = 0; - if (stream.total_out + block_header_skip != sz) { + if (br->zstream->total_out + block_header_skip != sz) { err = REFTABLE_FORMAT_ERROR; goto done; } @@ -242,7 +245,7 @@ int block_reader_init(struct block_reader *br, struct reftable_block *block, reftable_block_done(block); block->data = br->uncompressed_data; block->len = sz; - full_block_size = src_len + block_header_skip - stream.avail_in; + full_block_size = src_len + block_header_skip - br->zstream->avail_in; } else if (full_block_size == 0) { full_block_size = sz; } else if (sz < full_block_size && sz < block->len && @@ -275,6 +278,8 @@ done: void block_reader_release(struct block_reader *br) { + inflateEnd(br->zstream); + reftable_free(br->zstream); reftable_free(br->uncompressed_data); reftable_block_done(&br->block); } diff --git a/reftable/block.h b/reftable/block.h index 12414eb642..c1bd1892cb 100644 --- a/reftable/block.h +++ b/reftable/block.h @@ -56,6 +56,8 @@ int block_writer_finish(struct block_writer *w); /* clears out internally allocated block_writer members. */ void block_writer_release(struct block_writer *bw); +struct z_stream; + /* Read a block. */ struct block_reader { /* offset of the block header; nonzero for the first block in a @@ -67,6 +69,7 @@ struct block_reader { int hash_size; /* Uncompressed data for log entries. */ + z_stream *zstream; unsigned char *uncompressed_data; size_t uncompressed_cap; diff --git a/reftable/reader.c b/reftable/reader.c index aacd5f1337..481dff10d4 100644 --- a/reftable/reader.c +++ b/reftable/reader.c @@ -459,6 +459,7 @@ static int reader_seek_linear(struct table_iter *ti, * we would not do a linear search there anymore. */ memset(&next.br.block, 0, sizeof(next.br.block)); + next.br.zstream = NULL; next.br.uncompressed_data = NULL; next.br.uncompressed_cap = 0; -- cgit 1.2.3-korg