Ninja: set default pool depth for MS link.exe

mesonbuild/backend/ninjabackend.py

@@ -601,6 +601,15 @@ def detect_prefix(out):
 
         raise MesonException(f'Could not determine vs dep dependency prefix string. output: {stderr} {stdout}')
 
+    def get_link_pool_depth(self) -> int:
+        depth = self.environment.coredata.optstore.get_value('backend_max_links')
+        if depth == 0:
+            for compiler in self.environment.coredata.compilers.host.values():
+                d = compiler.linker.get_default_pool_depth()
+                if d > 0 and (depth == 0 or d < depth):
+                    depth = d
+        return depth;
+
     def generate(self, capture: bool = False, vslite_ctx: T.Optional[T.Dict] = None) -> T.Optional[T.Dict]:
         if vslite_ctx:
             # We don't yet have a use case where we'd expect to make use of this,
@@ -632,7 +641,7 @@ def generate(self, capture: bool = False, vslite_ctx: T.Optional[T.Dict] = None)
             outfile.write('# Do not edit by hand.\n\n')
             outfile.write('ninja_required_version = 1.8.2\n\n')
 
-            num_pools = self.environment.coredata.optstore.get_value('backend_max_links')
+            num_pools = self.get_link_pool_depth()
             if num_pools > 0:
                 outfile.write(f'''pool link_pool
   depth = {num_pools}
@@ -2305,7 +2314,7 @@ def _rsp_options(self, tool: T.Union['Compiler', 'StaticLinker', 'DynamicLinker'
         return options
 
     def generate_static_link_rules(self) -> None:
-        num_pools = self.environment.coredata.optstore.get_value('backend_max_links')
+        num_pools = self.get_link_pool_depth()
         if 'java' in self.environment.coredata.compilers.host:
             self.generate_java_link()
         for for_machine in MachineChoice:
@@ -2353,7 +2362,7 @@ def generate_static_link_rules(self) -> None:
             self.add_rule(NinjaRule(rule, cmdlist, args, description, **options, extra=pool))
 
     def generate_dynamic_link_rules(self) -> None:
-        num_pools = self.environment.coredata.optstore.get_value('backend_max_links')
+        num_pools = self.get_link_pool_depth()
         for for_machine in MachineChoice:
             complist = self.environment.coredata.compilers[for_machine]
             for langname, compiler in complist.items():

mesonbuild/linkers/linkers.py

@@ -298,6 +298,13 @@ def get_command_to_archive_shlib(self) -> T.List[str]:
         #Only used by AIX.
         return []
 
+    def get_default_pool_depth(self):
+        # Returns the ideal number of concurrent invocations.
+        # Returning 0 means no limit, so the default concurrency
+        # value (tipically the number of logical processors) is
+        # used
+        return 0
+
 
 if T.TYPE_CHECKING:
     StaticLinkerBase = StaticLinker
@@ -1368,6 +1375,12 @@ def get_win_subsystem_args(self, value: str) -> T.List[str]:
     def fatal_warnings(self) -> T.List[str]:
         return ['-WX']
 
+    def get_default_pool_depth(self):
+        # MS link.exe is internally multithreaded and uses lots of memory.
+        # we might check the amount of physical memory here, but it's not
+        # clear if parallel invocations of the linker bring any advantage.
+        return 1
+
 
 class ClangClDynamicLinker(VisualStudioLikeLinkerMixin, DynamicLinker):