2005-11-08 04:42:36

by Zachary Amsden

Subject: [PATCH 21/21] i386 Ldt context inline

I was also able to get the LDT switching functionality out of the
critical path in switch_mm, which reduces the number of function calls,
potential TLB misses and code size.

Signed-off-by: Zachary Amsden <[email protected]>
Index: linux-2.6.14-zach-work/include/asm-i386/desc.h
===================================================================
--- linux-2.6.14-zach-work.orig/include/asm-i386/desc.h 2005-11-05 02:30:35.000000000 -0800
+++ linux-2.6.14-zach-work/include/asm-i386/desc.h 2005-11-05 02:32:51.000000000 -0800
@@ -271,6 +271,9 @@ static inline void restore_bios_segments
put_cpu();
}

+extern void destroy_ldt(mm_context_t *pc);
+extern int copy_ldt(mm_context_t *new, mm_context_t *old);
+
#endif /* !__ASSEMBLY__ */

#endif
Index: linux-2.6.14-zach-work/include/asm-i386/mmu_context.h
===================================================================
--- linux-2.6.14-zach-work.orig/include/asm-i386/mmu_context.h 2005-11-05 02:30:35.000000000 -0800
+++ linux-2.6.14-zach-work/include/asm-i386/mmu_context.h 2005-11-05 02:32:51.000000000 -0800
@@ -10,9 +10,28 @@
/*
* Used for LDT copy/destruction.
*/
-int init_new_context(struct task_struct *tsk, struct mm_struct *mm);
-void destroy_context(struct mm_struct *mm);
+static inline int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+ struct mm_struct * old_mm;
+ int retval = 0;
+
+ memset(&mm->context, 0, sizeof(mm->context));
+ init_MUTEX(&mm->context.sem);
+ old_mm = current->mm;
+ if (old_mm && unlikely(old_mm->context.ldt)) {
+ retval = copy_ldt(&mm->context, &old_mm->context);
+ }
+ return retval;
+}

+/*
+ * No need to lock the MM as we are the last user
+ */
+static inline void destroy_context(struct mm_struct *mm)
+{
+ if (unlikely(mm->context.ldt))
+ destroy_ldt(&mm->context);
+}

static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
{
Index: linux-2.6.14-zach-work/arch/i386/kernel/ldt.c
===================================================================
--- linux-2.6.14-zach-work.orig/arch/i386/kernel/ldt.c 2005-11-05 02:32:28.000000000 -0800
+++ linux-2.6.14-zach-work/arch/i386/kernel/ldt.c 2005-11-05 02:33:24.000000000 -0800
@@ -103,29 +103,6 @@ void destroy_ldt(mm_context_t *pc)
pc->ldt = NULL;
}

-int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
-{
- struct mm_struct * old_mm;
- int retval = 0;
-
- memset(&mm->context, 0, sizeof(mm->context));
- init_MUTEX(&mm->context.sem);
- old_mm = current->mm;
- if (old_mm && unlikely(old_mm->context.ldt)) {
- retval = copy_ldt(&mm->context, &old_mm->context);
- }
- return retval;
-}
-
-/*
- * No need to lock the MM as we are the last user
- */
-void destroy_context(struct mm_struct *mm)
-{
- if (unlikely(mm->context.ldt))
- destroy_ldt(&mm->context);
-}
-
static int read_ldt(void __user * ptr, unsigned long bytecount)
{
int err;

2005-11-08 07:46:34

by Ingo Molnar

Subject: Re: [PATCH 21/21] i386 Ldt context inline

* Zachary Amsden <[email protected]> wrote:

> + if (old_mm && unlikely(old_mm->context.ldt)) {
> + retval = copy_ldt(&mm->context, &old_mm->context);
> + }

style police: remove the { }. You only moved the function, but still :-)

Ingo

2005-11-10 14:12:00

by Andi Kleen

Subject: Re: [PATCH 21/21] i386 Ldt context inline

On Tuesday 08 November 2005 05:42, Zachary Amsden wrote:
> I was also able to get the LDT switching functionality out of the
> critical path in switch_mm, which reduces the number of function calls,
> potential TLB misses and code size.

Hmm - i don't think your description matches the patch. Or where is
the critical path here?

-Andi