forall: greatly speed up processing overhead

With the recent commit 0501b29e7a
("status: Use multiprocessing for `repo status -j<num>` instead of
threading"), the limitation with project serialization no longer
applies.  It turns out that ad-hoc logic is expensive.  In the CrOS
checkout (~1000 projects w/8 jobs by default), it adds about ~7sec
overhead to all invocations.  With a fast nop run:
	time repo forall -j8 -c true
This goes from ~11sec to ~4sec -- more than 50% speedup.

Change-Id: Ie6bcccd21eef20440692751b7ebd36c890d5bbcc
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/298724
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

subcmds/forall.py

@@ -158,31 +158,6 @@ without iterating through the remaining projects.
   def WantPager(self, opt):
     return opt.project_header and opt.jobs == 1
 
-  def _SerializeProject(self, project):
-    """ Serialize a project._GitGetByExec instance.
-
-    project._GitGetByExec is not pickle-able. Instead of trying to pass it
-    around between processes, make a dict ourselves containing only the
-    attributes that we need.
-
-    """
-    if not self.manifest.IsMirror:
-      lrev = project.GetRevisionId()
-    else:
-      lrev = None
-    return {
-        'name': project.name,
-        'relpath': project.relpath,
-        'remote_name': project.remote.name,
-        'lrev': lrev,
-        'rrev': project.revisionExpr,
-        'annotations': dict((a.name, a.value) for a in project.annotations),
-        'gitdir': project.gitdir,
-        'worktree': project.worktree,
-        'upstream': project.upstream,
-        'dest_branch': project.dest_branch,
-    }
-
   def ValidateOptions(self, opt, args):
     if not opt.command:
       self.Usage()
@@ -242,7 +217,7 @@ without iterating through the remaining projects.
       with multiprocessing.Pool(opt.jobs, InitWorker) as pool:
         results_it = pool.imap(
             functools.partial(DoWorkWrapper, mirror, opt, cmd, shell, config),
-            enumerate(self._SerializeProject(x) for x in projects),
+            enumerate(projects),
             chunksize=WORKER_BATCH_SIZE)
         first = True
         for (r, output) in results_it:
@@ -292,7 +267,7 @@ def DoWorkWrapper(mirror, opt, cmd, shell, config, args):
   try:
     return DoWork(project, mirror, opt, cmd, shell, cnt, config)
   except KeyboardInterrupt:
-    print('%s: Worker interrupted' % project['name'])
+    print('%s: Worker interrupted' % project.name)
     raise WorkerKeyboardInterrupt()
 
 
@@ -304,22 +279,22 @@ def DoWork(project, mirror, opt, cmd, shell, cnt, config):
       val = ''
     env[name] = val
 
-  setenv('REPO_PROJECT', project['name'])
+  setenv('REPO_PROJECT', project.name)
-  setenv('REPO_PATH', project['relpath'])
+  setenv('REPO_PATH', project.relpath)
-  setenv('REPO_REMOTE', project['remote_name'])
+  setenv('REPO_REMOTE', project.remote.name)
-  setenv('REPO_LREV', project['lrev'])
+  setenv('REPO_LREV', '' if mirror else project.GetRevisionId())
-  setenv('REPO_RREV', project['rrev'])
+  setenv('REPO_RREV', project.revisionExpr)
-  setenv('REPO_UPSTREAM', project['upstream'])
+  setenv('REPO_UPSTREAM', project.upstream)
-  setenv('REPO_DEST_BRANCH', project['dest_branch'])
+  setenv('REPO_DEST_BRANCH', project.dest_branch)
   setenv('REPO_I', str(cnt + 1))
-  for name in project['annotations']:
+  for annotation in project.annotations:
-    setenv("REPO__%s" % (name), project['annotations'][name])
+    setenv("REPO__%s" % (annotation.name), annotation.value)
 
   if mirror:
-    setenv('GIT_DIR', project['gitdir'])
+    setenv('GIT_DIR', project.gitdir)
-    cwd = project['gitdir']
+    cwd = project.gitdir
   else:
-    cwd = project['worktree']
+    cwd = project.worktree
 
   if not os.path.exists(cwd):
     # Allow the user to silently ignore missing checkouts so they can run on
@@ -330,7 +305,7 @@ def DoWork(project, mirror, opt, cmd, shell, cnt, config):
     output = ''
     if ((opt.project_header and opt.verbose)
             or not opt.project_header):
-      output = 'skipping %s/' % project['relpath']
+      output = 'skipping %s/' % project.relpath
     return (1, output)
 
   if opt.verbose:
@@ -350,9 +325,9 @@ def DoWork(project, mirror, opt, cmd, shell, cnt, config):
       out = ForallColoring(config)
       out.redirect(buf)
       if mirror:
-        project_header_path = project['name']
+        project_header_path = project.name
       else:
-        project_header_path = project['relpath']
+        project_header_path = project.relpath
       out.project('project %s/' % project_header_path)
       out.nl()
       buf.write(output)