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fast-import: treat SIGUSR1 as a request to access objects early

It can be tedious to wait for a multi-million-revision import. Unfortunately it is hard to spy on the import because fast-import works by continuously streaming out objects, without updating the pack index or refs until a checkpoint command or the end of the stream. So allow the impatient operator to request checkpoints by sending a signal, like so: killall -USR1 git-fast-import When receiving such a signal, fast-import would schedule a checkpoint to take place after the current top-level command (usually a "commit" or "blob" request) finishes. Caveats: just like ordinary checkpoint commands, such requests slow down the import. Switching to a new pack at a suboptimal moment is also likely to result in a less dense initial collection of packs. That's the price. Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jonathan Nieder committed Nov 22, 2010 at 02:16 UTC dc01f59d21fca9ade97f1433ca4cee17b5ce59a7

2 files changed +47 -1

Documentation/git-fast-import.txt

@@ -1233,6 +1233,13 @@ and lazy loading of subtrees, allows fast-import to efficiently import

1233 projects with 2,000+ branches and 45,114+ files in a very limited

1234 memory footprint (less than 2.7 MiB per active branch).

1235

1236 +Signals

1237 +-------

1238 +Sending *SIGUSR1* to the 'git fast-import' process ends the current

1239 +packfile early, simulating a `checkpoint` command. The impatient

1240 +operator can use this facility to peek at the objects and refs from an

1241 +import in progress, at the cost of some added running time and worse

1242 +compression.

1243

1244 Author

1245 ------

fast-import.c

+40 -1

@@ -361,6 +361,9 @@ static uintmax_t next_mark;

361 static struct strbuf new_data = STRBUF_INIT;

362 static int seen_data_command;

363

364 +/* Signal handling */

365 +static volatile sig_atomic_t checkpoint_requested;

366 +

367 static void parse_argv(void);

368

369 static void write_branch_report(FILE *rpt, struct branch *b)

@@ -500,6 +503,32 @@ static NORETURN void die_nicely(const char *err, va_list params)

503 exit(128);

504 }

505

506 +#ifndef SIGUSR1 /* Windows, for example */

507 +

508 +static void set_checkpoint_signal(void)

509 +{

510 +}

511 +

512 +#else

513 +

514 +static void checkpoint_signal(int signo)

515 +{

516 + checkpoint_requested = 1;

517 +}

518 +

519 +static void set_checkpoint_signal(void)

520 +{

521 + struct sigaction sa;

522 +

523 + memset(&sa, 0, sizeof(sa));

524 + sa.sa_handler = checkpoint_signal;

525 + sigemptyset(&sa.sa_mask);

526 + sa.sa_flags = SA_RESTART;

527 + sigaction(SIGUSR1, &sa, NULL);

528 +}

529 +

530 +#endif

531 +

532 static void alloc_objects(unsigned int cnt)

533 {

534 struct object_entry_pool *b;

@@ -2689,14 +2718,20 @@ static void parse_reset_branch(void)

2718 unread_command_buf = 1;

2719 }

2720

2692 -static void parse_checkpoint(void)

2721 +static void checkpoint(void)

2722 {

2723 + checkpoint_requested = 0;

2724 if (object_count) {

2725 cycle_packfile();

2726 dump_branches();

2727 dump_tags();

2728 dump_marks();

2729 }

2730 +}

2731 +

2732 +static void parse_checkpoint(void)

2733 +{

2734 + checkpoint_requested = 1;

2735 skip_optional_lf();

2736 }

2737

@@ -2953,6 +2988,7 @@ int main(int argc, const char **argv)

2988 prepare_packed_git();

2989 start_packfile();

2990 set_die_routine(die_nicely);

2991 + set_checkpoint_signal();

2992 while (read_next_command() != EOF) {

2993 if (!strcmp("blob", command_buf.buf))

2994 parse_new_blob();

@@ -2974,6 +3010,9 @@ int main(int argc, const char **argv)

3010 /* ignore non-git options*/;

3011 else

3012 die("Unsupported command: %s", command_buf.buf);

3013 +

3014 + if (checkpoint_requested)

3015 + checkpoint();

3016 }

3017

3018 /* argv hasn't been parsed yet, do so */