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[2a01:4f8:120:2468::2]) by smtp.gmail.com with ESMTPSA id ds5-20020a170907724500b006df8f39dadesm7006601ejc.218.2022.03.29.06.56.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Mar 2022 06:56:18 -0700 (PDT) From: =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?= To: git@vger.kernel.org Cc: Junio C Hamano , Han Xin , Jiang Xin , =?UTF-8?q?Ren=C3=A9=20Scharfe?= , Derrick Stolee , Philip Oakley , Neeraj Singh , Elijah Newren , Han Xin , Jiang Xin , =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?= Subject: [PATCH v12 1/8] unpack-objects: low memory footprint for get_data() in dry_run mode Date: Tue, 29 Mar 2022 15:56:06 +0200 Message-Id: X-Mailer: git-send-email 2.35.1.1548.g36973b18e52 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Han Xin As the name implies, "get_data(size)" will allocate and return a given amount of memory. Allocating memory for a large blob object may cause the system to run out of memory. Before preparing to replace calling of "get_data()" to unpack large blob objects in latter commits, refactor "get_data()" to reduce memory footprint for dry_run mode. Because in dry_run mode, "get_data()" is only used to check the integrity of data, and the returned buffer is not used at all, we can allocate a smaller buffer and reuse it as zstream output. Therefore, in dry_run mode, "get_data()" will release the allocated buffer and return NULL instead of returning garbage data. The "find [...]objects/?? -type f | wc -l" test idiom being used here is adapted from the same "find" use added to another test in d9545c7f465 (fast-import: implement unpack limit, 2016-04-25). Suggested-by: Jiang Xin Signed-off-by: Han Xin Signed-off-by: Ævar Arnfjörð Bjarmason --- builtin/unpack-objects.c | 34 ++++++++++++++++++--------- t/t5351-unpack-large-objects.sh | 41 +++++++++++++++++++++++++++++++++ 2 files changed, 64 insertions(+), 11 deletions(-) create mode 100755 t/t5351-unpack-large-objects.sh diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c index dbeb0680a58..e3d30025979 100644 --- a/builtin/unpack-objects.c +++ b/builtin/unpack-objects.c @@ -96,15 +96,26 @@ static void use(int bytes) display_throughput(progress, consumed_bytes); } +/* + * Decompress zstream from stdin and return specific size of data. + * The caller is responsible to free the returned buffer. + * + * But for dry_run mode, "get_data()" is only used to check the + * integrity of data, and the returned buffer is not used at all. + * Therefore, in dry_run mode, "get_data()" will release the small + * allocated buffer which is reused to hold temporary zstream output + * and return NULL instead of returning garbage data. + */ static void *get_data(unsigned long size) { git_zstream stream; - void *buf = xmallocz(size); + unsigned long bufsize = dry_run && size > 8192 ? 8192 : size; + void *buf = xmallocz(bufsize); memset(&stream, 0, sizeof(stream)); stream.next_out = buf; - stream.avail_out = size; + stream.avail_out = bufsize; stream.next_in = fill(1); stream.avail_in = len; git_inflate_init(&stream); @@ -124,8 +135,15 @@ static void *get_data(unsigned long size) } stream.next_in = fill(1); stream.avail_in = len; + if (dry_run) { + /* reuse the buffer in dry_run mode */ + stream.next_out = buf; + stream.avail_out = bufsize; + } } git_inflate_end(&stream); + if (dry_run) + FREE_AND_NULL(buf); return buf; } @@ -325,10 +343,8 @@ static void unpack_non_delta_entry(enum object_type type, unsigned long size, { void *buf = get_data(size); - if (!dry_run && buf) + if (buf) write_object(nr, type, buf, size); - else - free(buf); } static int resolve_against_held(unsigned nr, const struct object_id *base, @@ -358,10 +374,8 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size, oidread(&base_oid, fill(the_hash_algo->rawsz)); use(the_hash_algo->rawsz); delta_data = get_data(delta_size); - if (dry_run || !delta_data) { - free(delta_data); + if (!delta_data) return; - } if (has_object_file(&base_oid)) ; /* Ok we have this one */ else if (resolve_against_held(nr, &base_oid, @@ -397,10 +411,8 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size, die("offset value out of bound for delta base object"); delta_data = get_data(delta_size); - if (dry_run || !delta_data) { - free(delta_data); + if (!delta_data) return; - } lo = 0; hi = nr; while (lo < hi) { diff --git a/t/t5351-unpack-large-objects.sh b/t/t5351-unpack-large-objects.sh new file mode 100755 index 00000000000..8d84313221c --- /dev/null +++ b/t/t5351-unpack-large-objects.sh @@ -0,0 +1,41 @@ +#!/bin/sh +# +# Copyright (c) 2022 Han Xin +# + +test_description='git unpack-objects with large objects' + +. ./test-lib.sh + +prepare_dest () { + test_when_finished "rm -rf dest.git" && + git init --bare dest.git +} + +test_expect_success "create large objects (1.5 MB) and PACK" ' + test-tool genrandom foo 1500000 >big-blob && + test_commit --append foo big-blob && + test-tool genrandom bar 1500000 >big-blob && + test_commit --append bar big-blob && + PACK=$(echo HEAD | git pack-objects --revs pack) +' + +test_expect_success 'set memory limitation to 1MB' ' + GIT_ALLOC_LIMIT=1m && + export GIT_ALLOC_LIMIT +' + +test_expect_success 'unpack-objects failed under memory limitation' ' + prepare_dest && + test_must_fail git -C dest.git unpack-objects err && + grep "fatal: attempting to allocate" err +' + +test_expect_success 'unpack-objects works with memory limitation in dry-run mode' ' + prepare_dest && + git -C dest.git unpack-objects -n