x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86
Don't burden architectures without dynamic task_struct sizing
with the overhead of dynamic sizing.
Also optimize the x86 code a bit by caching task_struct_size.
Acked-and-Tested-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1437128892-9831-3-git-send-email-mingo@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/fork.c b/kernel/fork.c
index 431b67a..dbd9b8d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -287,21 +287,20 @@
max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
}
-int __weak arch_task_struct_size(void)
-{
- return sizeof(struct task_struct);
-}
+#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
+/* Initialized by the architecture: */
+int arch_task_struct_size __read_mostly;
+#endif
void __init fork_init(void)
{
- int task_struct_size = arch_task_struct_size();
#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
#ifndef ARCH_MIN_TASKALIGN
#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
#endif
/* create a slab on which task_structs can be allocated */
task_struct_cachep =
- kmem_cache_create("task_struct", task_struct_size,
+ kmem_cache_create("task_struct", arch_task_struct_size,
ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
#endif