[Context] Add option for context alignment

emper/Common.hpp

@@ -30,7 +30,7 @@ using func_t = std::function<void()>;
 #define likely(x) __builtin_expect(!!(x), 1)
 #define unlikely(x) __builtin_expect(!!(x), 0)
 
-#define CACHE_LINE_SIZE 64
+#define CACHE_LINE_SIZE EMPER_ASSUME_CACHE_LINE_SIZE
 #define ALIGN_TO_CACHE_LINE alignas(CACHE_LINE_SIZE)
 #define CACHE_LINE_EXCLUSIVE(T, symbol)                                          \
 	std::aligned_storage<CACHE_LINE_SIZE, CACHE_LINE_SIZE>::type __##symbol##_mem; \

emper/Context.hpp

@@ -13,6 +13,7 @@
 #include "Common.hpp"	 // for func_t, DIE, ALIGN_TO_CACHE_LINE
 #include "Debug.hpp"	 // for LOGD, LogSubsystem, LogSubsystem::C, Logger
 #include "Emper.hpp"	 // for Emper::DEBUG
+#include "emper-config.h"
 #include "lib/math.hpp"
 
 class AbstractFiber;
@@ -29,7 +30,7 @@ extern "C" [[noreturn]] void switch_and_load_context(void** toTos);
 extern "C" void save_and_switch_context(void** toTos, void** fromTos);
 extern "C" [[noreturn]] void switch_context(void** toTos);
 
-class ALIGN_TO_CACHE_LINE Context : Logger<LogSubsystem::C> {
+class EMPER_CONTEXT_ALIGNAS Context : Logger<LogSubsystem::C> {
  private:
 	static constexpr size_t CONTEXT_SIZE =
 			em::roundUp(emper::MIN_CONTEXT_STACK_SIZE, emper::ASSUME_PAGE_SIZE);

emper/Emper.hpp

@@ -283,4 +283,6 @@ static const size_t ASSUME_PAGE_SIZE = EMPER_ASSUME_PAGE_SIZE;
 
 static const size_t MIN_CONTEXT_STACK_SIZE = EMPER_MIN_CONTEXT_STACK_SIZE;
 
+static const size_t ASSUME_CACHE_LINE_SIZE = EMPER_ASSUME_CACHE_LINE_SIZE;
+
 }	 // namespace emper

eval/SpawnALot.cpp

 // SPDX-License-Identifier: LGPL-3.0-or-later
-// Copyright © 2020 Florian Schmaus
+// Copyright © 2020-2022 Florian Schmaus
 #include <chrono>		 // for nanoseconds, time_point, dur...
 #include <cstdint>	 // for uint8_t, uint64_t
 #include <cstdlib>	 // for EXIT_SUCCESS
 #include <iostream>	 // for operator<<, basic_ostream
 #include <thread>		 // for thread
 
-#include "BinaryPrivateSemaphore.hpp"		 // for BPS
+#include "BinaryPrivateSemaphore.hpp"
+#include "Common.hpp"
 #include "CountingPrivateSemaphore.hpp"	 // for CPS
 #include "Fiber.hpp"										 // for Fiber
 #include "PrivateSemaphore.hpp"					 // for PS
@@ -14,8 +15,6 @@
 #include "emper-common.h"								 // for UNUSED_ARG
 #include "lib/DebugUtil.hpp"						 // for enableStacktraceOnAborts
 
-#define CACHE_LINE_SIZE 64
-
 static void spawnALotThreadsRecursiveTFun(unsigned int depth, unsigned int width,
 																					unsigned int current_depth) {
 	if (current_depth == depth) return;

meson.build

@@ -54,6 +54,8 @@ endif
 
 continuation_stealing_mode = get_option('continuation_stealing_mode')
 locked_ws_queue = get_option('locked_ws_queue')
+assume_page_size = get_option('assume_page_size')
+assume_cache_line_size = get_option('assume_cache_line_size')
 
 conf_data.set('EMPER_WORKER_SLEEP', get_option('worker_sleep'))
 conf_data.set('EMPER_WORKER_WAKEUP_STRATEGY', get_option('worker_wakeup_strategy'))
@@ -70,8 +72,21 @@ conf_data.set('EMPER_CONTINUATION_STEALING_MODE', continuation_stealing_mode)
 conf_data.set('EMPER_CONTINUATION_STEALING_MADVISE_STACK', get_option('continuation_stealing_madvise_stack'))
 conf_data.set('EMPER_BUILD_WITH_CLANG', cpp_is_clang)
 conf_data.set('EMPER_CONTEXT_MANAGER_WITH_MEMORY_MANAGER', get_option('context_manager_with_memory_manager'))
-conf_data.set('EMPER_ASSUME_PAGE_SIZE', get_option('assume_page_size'))
+conf_data.set('EMPER_ASSUME_PAGE_SIZE', assume_page_size)
 conf_data.set('EMPER_MIN_CONTEXT_STACK_SIZE', get_option('min_context_stack_size'))
+conf_data.set('EMPER_ASSUME_CACHE_LINE_SIZE', assume_cache_line_size)
+
+context_alignment = get_option('context_alignment')
+if context_alignment == 'none'
+  context_alignas = ''
+elif context_alignment == 'cache_line_size'
+  context_alignas = 'alignas(' + cache_line_size + ')'
+elif context_alignment == 'page_size'
+  context_alignas = 'alignas(' + page_size + ')'
+else
+  error('Unknown context alignment option: ' + context_alignment)
+endif
+conf_data.set('EMPER_CONTEXT_ALIGNAS', context_alignas)
 
 if continuation_stealing_mode == 'locked' and not locked_ws_queue
   error('*Locked* continuation stealing only works with locked work-stealing queues (locked_ws_queue=true)')

meson_options.txt

@@ -251,3 +251,17 @@ option(
   value: 65536,
   min: 1,
 )
+option(
+  'context_alignment',
+  type: 'combo',
+  description: 'Use the select mechanism to determine the alignment of contexts',
+  choices: ['none', 'cache_line_size', 'page_size'],
+  value: 'none',
+)
+option(
+  'assume_cache_line_size',
+  type: 'integer',
+  description: 'Assume the given cache-line size in bytes',
+  value: 64,
+  min: 1,
+)