[PATCH] fast-import: implement --min-pack-size parameter

From

EWEric Wong <normalperson@yhbt.net>

Date

Apr 23, 2016, 02:42 UTC

Message-ID

<20160423024225.GA4293@dcvr.yhbt.net>

Signed-off-by: Eric Wong <normalperson@yhbt.net>
---
  There should be a matching config file directive, but I'm
  not sure how/if it should affect other commands.  So I'm
  not sure if it should be "pack.packSizeMin" or
  "fastimport.packSizeMin" or something else.

  To further reduce disk I/O, the fsync_or_die call in
  fixup_pack_header_footer could probably be moved out of that
  function and become the fphf caller's responsibility.

 Documentation/git-fast-import.txt   |  9 ++++++++
 fast-import.c                       | 30 ++++++++++++++++++++++++++
 t/t9302-fast-import-min-packsize.sh | 42 +++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+)
 create mode 100755 t/t9302-fast-import-min-packsize.sh

diff --git a/Documentation/git-fast-import.txt b/Documentation/git-fast-import.txt
index 66910aa..8c0ac94 100644
--- a/Documentation/git-fast-import.txt
+++ b/Documentation/git-fast-import.txt
@@ -136,6 +136,15 @@ Performance and Compression Tuning
 	Maximum size of each output packfile.
 	The default is unlimited.
 
+--min-pack-size=<n>::
+	Mininum size of an output packfile, packfiles smaller
+	than this threshold are unpacked into loose objects and
+	the pack is discarded.  This is useful when performing
+	small, incremental imports as loose objects and relying
+	on `git gc --auto` may be more efficient than generating
+	many tiny packs.
+	The default is to always preserve the pack and never
+	generate loose objects.
 
 Performance
 -----------
diff --git a/fast-import.c b/fast-import.c
index 9fc7093..a00bee5 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -166,6 +166,7 @@ Format of STDIN stream:
 #include "quote.h"
 #include "exec_cmd.h"
 #include "dir.h"
+#include "run-command.h"
 
 #define PACK_ID_BITS 16
 #define MAX_PACK_ID ((1<<PACK_ID_BITS)-1)
@@ -282,6 +283,7 @@ struct recent_command {
 /* Configured limits on output */
 static unsigned long max_depth = 10;
 static off_t max_packsize;
+static off_t min_packsize;
 static int force_update;
 static int pack_compression_level = Z_DEFAULT_COMPRESSION;
 static int pack_compression_seen;
@@ -950,6 +952,22 @@ static void unkeep_all_packs(void)
 	}
 }
 
+static int loosen_small_pack(const struct packed_git *p)
+{
+	struct child_process unpack = CHILD_PROCESS_INIT;
+
+	if (lseek(p->pack_fd, 0, SEEK_SET) < 0)
+		die_errno("Failed seeking to start of '%s'", p->pack_name);
+
+	unpack.in = p->pack_fd;
+	unpack.git_cmd = 1;
+	unpack.stdout_to_stderr = 1;
+	argv_array_push(&unpack.args, "unpack-objects");
+	argv_array_push(&unpack.args, "-q");
+
+	return run_command(&unpack);
+}
+
 static void end_packfile(void)
 {
 	static int running;
@@ -972,6 +990,12 @@ static void end_packfile(void)
 		fixup_pack_header_footer(pack_data->pack_fd, pack_data->sha1,
 				    pack_data->pack_name, object_count,
 				    cur_pack_sha1, pack_size);
+
+		if (pack_size < min_packsize) {
+			if (loosen_small_pack(pack_data) == 0)
+				goto discard_pack;
+		}
+
 		close(pack_data->pack_fd);
 		idx_name = keep_pack(create_index());
 
@@ -1002,6 +1026,7 @@ static void end_packfile(void)
 		pack_id++;
 	}
 	else {
+discard_pack:
 		close(pack_data->pack_fd);
 		unlink_or_warn(pack_data->pack_name);
 	}
@@ -3237,6 +3262,11 @@ static int parse_one_option(const char *option)
 			v = 1024 * 1024;
 		}
 		max_packsize = v;
+	} else if (skip_prefix(option, "min-pack-size=", &option)) {
+		unsigned long v;
+		if (!git_parse_ulong(option, &v))
+			return 0;
+		min_packsize = v;
 	} else if (skip_prefix(option, "big-file-threshold=", &option)) {
 		unsigned long v;
 		if (!git_parse_ulong(option, &v))
diff --git a/t/t9302-fast-import-min-packsize.sh b/t/t9302-fast-import-min-packsize.sh
new file mode 100755
index 0000000..7dcdccc
--- /dev/null
+++ b/t/t9302-fast-import-min-packsize.sh
@@ -0,0 +1,42 @@
+#!/bin/sh
+test_description='test git fast-import min-packsize'
+. ./test-lib.sh
+
+test_expect_success 'create loose objects on import' '
+	test_tick &&
+	cat >input <<-INPUT_END &&
+	commit refs/heads/master
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	initial
+	COMMIT
+
+	done
+	INPUT_END
+
+	git fast-import --done --min-pack-size=1g <input &&
+	git fsck --no-progress &&
+	test $(find .git/objects/?? -type f | wc -l) -eq 2 &&
+	test $(find .git/objects/pack -type f | wc -l) -eq 0
+'
+
+test_expect_success 'bigger packs are preserved' '
+	test_tick &&
+	cat >input <<-INPUT_END &&
+	commit refs/heads/master
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	incremental should create a pack
+	COMMIT
+	from refs/heads/master^0
+
+	done
+	INPUT_END
+
+	git fast-import --done --min-pack-size=10 <input &&
+	git fsck --no-progress &&
+	test $(find .git/objects/?? -type f | wc -l) -eq 2 &&
+	test $(find .git/objects/pack -type f | wc -l) -eq 2
+'
+
+test_done

-- 
EW