Re: [PATCH 6/9] submodule: helper to run foreach in parallel

> Similar to `git submodule foreach` the new command `git submodule
> foreach_parallel` will run a command on each submodule.
>
> The commands are run in parallel up to the number of cores by default,
> or you can specify '-j 4' tun just run with 4 threads for example.
>
> One major difference to `git submodule foreach` is the handling of input
> and output to the commands. Because of the parallel nature of the execution
> it is not trivial how to schedule the std{in,out,err} channel for submodule
> the command is run in. So in this patch there is no support for stdin.
> stdout will be piped to stderr. stderr will make use of the synchronized
> output feature of run_command.
>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>  builtin/submodule--helper.c  | 133 ++++++++++++++++++++++++++++++++++++++++++-
>  git-submodule.sh             |  11 +++-
>  t/t7407-submodule-foreach.sh |  11 ++++
>  3 files changed, 153 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> index d29499c..18b67f0 100644
> --- a/builtin/submodule--helper.c
> +++ b/builtin/submodule--helper.c
> @@ -8,6 +8,7 @@
>  #include "submodule.h"
>  #include "submodule-config.h"
>  #include "string-list.h"
> +#include "thread-utils.h"
>  #include "run-command.h"
>
>  static const struct cache_entry **ce_entries;
> @@ -266,6 +267,127 @@ static int module_clone(int argc, const char **argv, const char *prefix)
>         return 0;
>  }
>
> +#ifndef NO_PTHREADS
> +struct submodule_args {
> +       const char *name;
> +       const char *path;
> +       const char *sha1;
> +       const char *toplevel;
> +       const char *prefix;
> +       const char **cmd;
> +       pthread_mutex_t *sync;
> +};
> +
> +int run_cmd_submodule(struct task_queue *aq, void *task)
> +{
> +       int i;
> +       struct submodule_args *args = task;
> +       struct strbuf out = STRBUF_INIT;
> +       struct strbuf sb = STRBUF_INIT;
> +       struct child_process *cp = xmalloc(sizeof(*cp));
> +
> +       strbuf_addf(&out, N_("Entering %s\n"), relative_path(args->path, args->prefix, &sb));
> +
> +       child_process_init(cp);
> +       argv_array_pushv(&cp->args, args->cmd);
> +
> +       argv_array_pushf(&cp->env_array, "name=%s", args->name);
> +       argv_array_pushf(&cp->env_array, "path=%s", args->path);
> +       argv_array_pushf(&cp->env_array, "sha1=%s", args->sha1);
> +       argv_array_pushf(&cp->env_array, "toplevel=%s", args->toplevel);
> +
> +       for (i = 0; local_repo_env[i]; i++)
> +               argv_array_push(&cp->env_array, local_repo_env[i]);
> +
> +       cp->no_stdin = 1;
> +       cp->out = 0;
> +       cp->err = -1;
> +       cp->dir = args->path;
> +       cp->stdout_to_stderr = 1;
> +       cp->use_shell = 1;
> +       cp->sync_mutex = args->sync;
> +       cp->sync_buf = &out;
> +
> +       return run_command(cp);
> +}
> +
> +int module_foreach_parallel(int argc, const char **argv, const char *prefix)
> +{
> +       int i, recursive = 0, number_threads = 0, quiet = 0;
> +       static struct pathspec pathspec;
> +       struct strbuf sb = STRBUF_INIT;
> +       struct task_queue *aq;
> +       char **cmd;
> +       const char **nullargv = {NULL};
> +       pthread_mutex_t mutex;
> +
> +       struct option module_update_options[] = {
> +               OPT_STRING(0, "prefix", &alternative_path,
> +                          N_("path"),
> +                          N_("alternative anchor for relative paths")),
> +               OPT_STRING(0, "cmd", &cmd,
> +                          N_("string"),
> +                          N_("command to run")),
> +               OPT_BOOL('r', "--recursive", &recursive,
> +                        N_("Recurse into nexted submodules")),
> +               OPT_INTEGER('j', "jobs", &number_threads,
> +                           N_("Recurse into nexted submodules")),
> +               OPT__QUIET(&quiet, N_("Suppress output")),
> +               OPT_END()
> +       };
> +
> +       static const char * const git_submodule_helper_usage[] = {
> +               N_("git submodule--helper foreach [--prefix=<path>] [<path>...]"),
> +               NULL
> +       };
> +
> +       argc = parse_options(argc, argv, prefix, module_update_options,
> +                            git_submodule_helper_usage, 0);
> +
> +       if (module_list_compute(0, nullargv, NULL, &pathspec) < 0)
> +               return 1;
> +
> +       gitmodules_config();
> +
> +       pthread_mutex_init(&mutex, NULL);
> +       aq = create_task_queue(number_threads);
> +
> +       for (i = 0; i < ce_used; i++) {
> +               const struct submodule *sub;
> +               const struct cache_entry *ce = ce_entries[i];
> +               struct submodule_args *args = malloc(sizeof(*args));
> +
> +               if (ce_stage(ce))
> +                       args->sha1 = xstrdup(sha1_to_hex(null_sha1));
> +               else
> +                       args->sha1 = xstrdup(sha1_to_hex(ce->sha1));
> +
> +               strbuf_reset(&sb);
> +               strbuf_addf(&sb, "%s/.git", ce->name);
> +               if (!file_exists(sb.buf)) {
> +                       free(args);
> +                       continue;
> +               }
> +
> +               args->path = ce->name;
> +               sub = submodule_from_path(null_sha1, args->path);
> +               if (!sub)
> +                       die("No submodule mapping found in .gitmodules for path '%s'", args->path);
> +
> +               args->name = sub->name;
> +               args->toplevel = xgetcwd();
> +               args->cmd = argv;
> +               args->sync = &mutex;
> +               args->prefix = alternative_path;
> +               add_task(aq, run_cmd_submodule, args);
> +       }
> +
> +       finish_task_queue(aq, NULL);
> +       pthread_mutex_destroy(&mutex);
> +       return 0;
> +}
> +#endif /* NO_PTHREADS */
> +
>  int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
>  {
>         if (argc < 2)
> @@ -280,7 +402,16 @@ int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
>         if (!strcmp(argv[1], "module_clone"))
>                 return module_clone(argc - 1, argv + 1, prefix);
>
> +#ifndef NO_PTHREADS
> +       if (!strcmp(argv[1], "foreach_parallel"))
> +               return module_foreach_parallel(argc - 1, argv + 1, prefix);
> +#endif
> +
>  usage:
>         usage("git submodule--helper [module_list | module_name | "
> -             "module_clone]\n");
> +             "module_clone"
> +#ifndef NO_PTHREADS
> +             " | foreach_parallel"
> +#endif
> +             "]\n");
>  }
> diff --git a/git-submodule.sh b/git-submodule.sh
> index fb5155e..f06488a 100755
> --- a/git-submodule.sh
> +++ b/git-submodule.sh
> @@ -431,6 +431,15 @@ cmd_foreach()
>  }
>
>  #
> +# Execute an arbitrary command sequence in each checked out
> +# submodule in parallel.
> +#
> +cmd_foreach_parallel()
> +{
> +       git submodule--helper foreach_parallel --prefix "$wt_prefix" $@
> +}
> +
> +#
>  # Register submodules in .git/config
>  #
>  # $@ = requested paths (default to all)
> @@ -1225,7 +1234,7 @@ cmd_sync()
>  while test $# != 0 && test -z "$command"
>  do
>         case "$1" in
> -       add | foreach | init | deinit | update | status | summary | sync)
> +       add | foreach | foreach_parallel | init | deinit | update | status | summary | sync)
>                 command=$1
>                 ;;
>         -q|--quiet)
> diff --git a/t/t7407-submodule-foreach.sh b/t/t7407-submodule-foreach.sh
> index 7ca10b8..16f6138 100755
> --- a/t/t7407-submodule-foreach.sh
> +++ b/t/t7407-submodule-foreach.sh
> @@ -195,6 +195,17 @@ test_expect_success 'test "foreach --quiet --recursive"' '
>         test_cmp expect actual
>  '
>
> +test_expect_success 'test "foreach_parallel --quiet"' '
> +       (
> +               cd clone2 &&
> +               git submodule foreach_parallel -q -- "echo \$name-\$path" > ../actual
> +       ) &&
> +       grep nested1-nested1 actual &&
> +       grep foo1-sub1 actual &&
> +       grep foo2-sub2 actual &&
> +       grep foo3-sub3 actual
> +'
> +

>  test_expect_success 'use "update --recursive" to checkout all submodules' '
>         git clone super clone3 &&
>         (
> --
> 2.5.0.264.g5e52b0d
>