From: Han Xin <hanxin.hx@xxxxxxxxxxxxxxx>
We used to call "get_data()" in "unpack_non_delta_entry()" to read the
entire contents of a blob object, no matter how big it is. This
implementation may consume all the memory and cause OOM.
By implementing a zstream version of input_stream interface, we can use
a small fixed buffer for "unpack_non_delta_entry()".
However, unpack non-delta objects from a stream instead of from an entrie
buffer will have 10% performance penalty. Therefore, only unpack object
larger than the "core.BigFileStreamingThreshold" in zstream. See the following
benchmarks:
hyperfine \
--setup \
'if ! test -d scalar.git; then git clone --bare https://github.com/microsoft/scalar.git; cp scalar.git/objects/pack/*.pack small.pack; fi' \
--prepare 'rm -rf dest.git && git init --bare dest.git'
Summary
'./git -C dest.git -c core.bigfilethreshold=512m unpack-objects <small.pack' in 'origin/master'
1.01 ± 0.04 times faster than './git -C dest.git -c core.bigfilethreshold=512m unpack-objects <small.pack' in 'HEAD~1'
1.01 ± 0.04 times faster than './git -C dest.git -c core.bigfilethreshold=512m unpack-objects <small.pack' in 'HEAD~0'
1.03 ± 0.10 times faster than './git -C dest.git -c core.bigfilethreshold=16k unpack-objects <small.pack' in 'origin/master'
1.02 ± 0.07 times faster than './git -C dest.git -c core.bigfilethreshold=16k unpack-objects <small.pack' in 'HEAD~0'
1.10 ± 0.04 times faster than './git -C dest.git -c core.bigfilethreshold=16k unpack-objects <small.pack' in 'HEAD~1'
Helped-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
Helped-by: Derrick Stolee <stolee@xxxxxxxxx>
Helped-by: Jiang Xin <zhiyou.jx@xxxxxxxxxxxxxxx>
Signed-off-by: Han Xin <hanxin.hx@xxxxxxxxxxxxxxx>
---
Documentation/config/core.txt | 11 +++++
builtin/unpack-objects.c | 70 ++++++++++++++++++++++++++++-
cache.h | 1 +
config.c | 5 +++
environment.c | 1 +
t/t5590-unpack-non-delta-objects.sh | 70 +++++++++++++++++++++++++++++
6 files changed, 157 insertions(+), 1 deletion(-)
create mode 100755 t/t5590-unpack-non-delta-objects.sh
diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt
index c04f62a54a..601b7a2418 100644
--- a/Documentation/config/core.txt
+++ b/Documentation/config/core.txt
@@ -424,6 +424,17 @@ be delta compressed, but larger binary media files won't be.
+
Common unit suffixes of 'k', 'm', or 'g' are supported.
+core.bigFileStreamingThreshold::
+ Files larger than this will be streamed out to a temporary
+ object file while being hashed, which will when be renamed
+ in-place to a loose object, particularly if the
+ `core.bigFileThreshold' setting dictates that they're always
+ written out as loose objects.
++
+Default is 128 MiB on all platforms.
++
+Common unit suffixes of 'k', 'm', or 'g' are supported.
+
core.excludesFile::
Specifies the pathname to the file that contains patterns to
describe paths that are not meant to be tracked, in addition
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index d878e2f8b4..0df115ab0d 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -326,11 +326,79 @@ static void added_object(unsigned nr, enum object_type type,
}
}
+struct input_zstream_data {
+ git_zstream *zstream;
+ unsigned char buf[8192];
+ int status;
+};
+
+static const void *feed_input_zstream(struct input_stream *in_stream, unsigned long *readlen)
+{
+ struct input_zstream_data *data = in_stream->data;
+ git_zstream *zstream = data->zstream;
+ void *in = fill(1);
+
+ if (!len || data->status == Z_STREAM_END) {
+ *readlen = 0;
+ return NULL;
+ }
+
+ zstream->next_out = data->buf;
+ zstream->avail_out = sizeof(data->buf);
+ zstream->next_in = in;
+ zstream->avail_in = len;
+
+ data->status = git_inflate(zstream, 0);
+ use(len - zstream->avail_in);
+ *readlen = sizeof(data->buf) - zstream->avail_out;
+
+ return data->buf;
+}
+
+static void write_stream_blob(unsigned nr, unsigned long size)
+{
+ git_zstream zstream;
+ struct input_zstream_data data;
+ struct input_stream in_stream = {
+ .read = feed_input_zstream,
+ .data = &data,
+ };
+ int ret;
+
+ memset(&zstream, 0, sizeof(zstream));
+ memset(&data, 0, sizeof(data));
+ data.zstream = &zstream;
+ git_inflate_init(&zstream);
+
+ if ((ret = write_object_file_flags(&in_stream, size, type_name(OBJ_BLOB) ,&obj_list[nr].oid, HASH_STREAM)))
+ die(_("failed to write object in stream %d"), ret);
+
+ if (zstream.total_out != size || data.status != Z_STREAM_END)
+ die(_("inflate returned %d"), data.status);
+ git_inflate_end(&zstream);
+
+ if (strict && !dry_run) {
+ struct blob *blob = lookup_blob(the_repository, &obj_list[nr].oid);
+ if (blob)
+ blob->object.flags |= FLAG_WRITTEN;
+ else
+ die("invalid blob object from stream");
+ }
+ obj_list[nr].obj = NULL;
+}
+
static void unpack_non_delta_entry(enum object_type type, unsigned long size,
unsigned nr)
{
- void *buf = get_data(size, dry_run);
+ void *buf;
+
+ /* Write large blob in stream without allocating full buffer. */
+ if (!dry_run && type == OBJ_BLOB && size > big_file_streaming_threshold) {
+ write_stream_blob(nr, size);
+ return;
+ }
+ buf = get_data(size, dry_run);
if (!dry_run && buf)
write_object(nr, type, buf, size);
else
diff --git a/cache.h b/cache.h
index 51bd435dea..78548cd67a 100644
--- a/cache.h
+++ b/cache.h
@@ -965,6 +965,7 @@ extern size_t packed_git_window_size;
extern size_t packed_git_limit;
extern size_t delta_base_cache_limit;
extern unsigned long big_file_threshold;
+extern unsigned long big_file_streaming_threshold;
extern unsigned long pack_size_limit_cfg;
/*
diff --git a/config.c b/config.c
index c5873f3a70..7b122a142a 100644
--- a/config.c
+++ b/config.c
@@ -1408,6 +1408,11 @@ static int git_default_core_config(const char *var, const char *value, void *cb)
return 0;
}
+ if (!strcmp(var, "core.bigfilestreamingthreshold")) {
+ big_file_streaming_threshold = git_config_ulong(var, value);
+ return 0;
+ }
+
if (!strcmp(var, "core.packedgitlimit")) {
packed_git_limit = git_config_ulong(var, value);
return 0;
diff --git a/environment.c b/environment.c
index 9da7f3c1a1..4fcc3de741 100644
--- a/environment.c
+++ b/environment.c
@@ -46,6 +46,7 @@ size_t packed_git_window_size = DEFAULT_PACKED_GIT_WINDOW_SIZE;
size_t packed_git_limit = DEFAULT_PACKED_GIT_LIMIT;
size_t delta_base_cache_limit = 96 * 1024 * 1024;
unsigned long big_file_threshold = 512 * 1024 * 1024;
+unsigned long big_file_streaming_threshold = 128 * 1024 * 1024;
int pager_use_color = 1;
const char *editor_program;
const char *askpass_program;
diff --git a/t/t5590-unpack-non-delta-objects.sh b/t/t5590-unpack-non-delta-objects.sh
new file mode 100755
index 0000000000..ff4c78900b
--- /dev/null
+++ b/t/t5590-unpack-non-delta-objects.sh
@@ -0,0 +1,70 @@
+#!/bin/sh
+#
+# Copyright (c) 2021 Han Xin
+#
+
+test_description='Test unpack-objects when receive pack'
+
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
+. ./test-lib.sh
+
+prepare_dest () {
+ test_when_finished "rm -rf dest.git" &&
+ git init --bare dest.git &&
+ git -C dest.git config core.bigFileStreamingThreshold $1
+ git -C dest.git config core.bigFileThreshold $1
+}
+
+test_expect_success "setup repo with big blobs (1.5 MB)" '
+ test-tool genrandom foo 1500000 >big-blob &&
+ test_commit --append foo big-blob &&
+ test-tool genrandom bar 1500000 >big-blob &&
+ test_commit --append bar big-blob &&
+ (
+ cd .git &&
+ find objects/?? -type f | sort
+ ) >expect &&
+ PACK=$(echo main | git pack-objects --revs test)
+'
+
+test_expect_success 'setup env: GIT_ALLOC_LIMIT to 1MB' '
+ GIT_ALLOC_LIMIT=1m &&
+ export GIT_ALLOC_LIMIT
+'
+
+test_expect_success 'fail to unpack-objects: cannot allocate' '
+ prepare_dest 2m &&
+ test_must_fail git -C dest.git unpack-objects <test-$PACK.pack 2>err &&
+ grep "fatal: attempting to allocate" err &&
+ (
+ cd dest.git &&
+ find objects/?? -type f | sort
+ ) >actual &&
+ test_file_not_empty actual &&
+ ! test_cmp expect actual
+'
+
+test_expect_success 'unpack big object in stream' '
+ prepare_dest 1m &&
+ git -C dest.git unpack-objects <test-$PACK.pack &&
+ git -C dest.git fsck &&
+ (
+ cd dest.git &&
+ find objects/?? -type f | sort
+ ) >actual &&
+ test_cmp expect actual
+'
+
+test_expect_success 'unpack-objects dry-run' '
+ prepare_dest 1m &&
+ git -C dest.git unpack-objects -n <test-$PACK.pack &&
+ (
+ cd dest.git &&
+ find objects/ -type f
+ ) >actual &&
+ test_must_be_empty actual
+'
+
+test_done
--
2.34.0
