* [PATCH 1/6] UML - Customize tlb.h
@ 2007-12-06 17:06 Jeff Dike
2007-12-06 19:46 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: Jeff Dike @ 2007-12-06 17:06 UTC (permalink / raw)
To: Andrew Morton; +Cc: LKML, uml-devel
Customize the hooks in tlb.h to optimize TLB flushing some more.
Add start and end fields to tlb_gather_mmu, which are used to limit
the address space range scanned when a region is unmapped.
The interfaces which just free page tables, without actually changing
mappings, don't need to cause a TLB flush.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
---
arch/um/kernel/tlb.c | 28 ++++++++---
include/asm-um/tlb.h | 121 ++++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 141 insertions(+), 8 deletions(-)
Index: linux-2.6-git/arch/um/kernel/tlb.c
===================================================================
--- linux-2.6-git.orig/arch/um/kernel/tlb.c 2007-12-06 10:34:31.000000000 -0500
+++ linux-2.6-git/arch/um/kernel/tlb.c 2007-12-06 10:34:41.000000000 -0500
@@ -193,18 +193,18 @@ static inline int update_pte_range(pmd_t
if (!pte_young(*pte)) {
r = 0;
w = 0;
- } else if (!pte_dirty(*pte)) {
+ } else if (!pte_dirty(*pte))
w = 0;
- }
+
prot = ((r ? UM_PROT_READ : 0) | (w ? UM_PROT_WRITE : 0) |
(x ? UM_PROT_EXEC : 0));
if (hvc->force || pte_newpage(*pte)) {
if (pte_present(*pte))
ret = add_mmap(addr, pte_val(*pte) & PAGE_MASK,
PAGE_SIZE, prot, hvc);
- else ret = add_munmap(addr, PAGE_SIZE, hvc);
- }
- else if (pte_newprot(*pte))
+ else
+ ret = add_munmap(addr, PAGE_SIZE, hvc);
+ } else if (pte_newprot(*pte))
ret = add_mprotect(addr, PAGE_SIZE, prot, hvc);
*pte = pte_mkuptodate(*pte);
} while (pte++, addr += PAGE_SIZE, ((addr != end) && !ret));
@@ -500,7 +500,8 @@ void flush_tlb_range(struct vm_area_stru
else fix_range(vma->vm_mm, start, end, 0);
}
-void flush_tlb_mm(struct mm_struct *mm)
+void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
+ unsigned long end)
{
/*
* Don't bother flushing if this address space is about to be
@@ -509,7 +510,20 @@ void flush_tlb_mm(struct mm_struct *mm)
if (atomic_read(&mm->mm_users) == 0)
return;
- fix_range(mm, 0, TASK_SIZE, 0);
+ fix_range(mm, start, end, 0);
+}
+
+void flush_tlb_mm(struct mm_struct *mm)
+{
+ struct vm_area_struct *vma = mm->mmap;
+
+ if (atomic_read(&mm->mm_users) == 0)
+ return;
+
+ while (vma != NULL) {
+ fix_range(mm, vma->vm_start, vma->vm_end, 0);
+ vma = vma->vm_next;
+ }
}
void force_flush_all(void)
Index: linux-2.6-git/include/asm-um/tlb.h
===================================================================
--- linux-2.6-git.orig/include/asm-um/tlb.h 2007-12-06 10:34:31.000000000 -0500
+++ linux-2.6-git/include/asm-um/tlb.h 2007-12-06 10:58:34.000000000 -0500
@@ -1,6 +1,125 @@
#ifndef __UM_TLB_H
#define __UM_TLB_H
-#include <asm/arch/tlb.h>
+#include <linux/swap.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+
+#define tlb_start_vma(tlb, vma) do { } while (0)
+#define tlb_end_vma(tlb, vma) do { } while (0)
+#define tlb_flush(tlb) flush_tlb_mm((tlb)->mm)
+
+/* struct mmu_gather is an opaque type used by the mm code for passing around
+ * any data needed by arch specific code for tlb_remove_page.
+ */
+struct mmu_gather {
+ struct mm_struct *mm;
+ unsigned int need_flush; /* Really unmapped some ptes? */
+ unsigned long start;
+ unsigned long end;
+ unsigned int fullmm; /* non-zero means full mm flush */
+};
+
+/* Users of the generic TLB shootdown code must declare this storage space. */
+DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
+
+static inline void __tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep,
+ unsigned long address)
+{
+ if (tlb->start > address)
+ tlb->start = address;
+ if (tlb->end < address + PAGE_SIZE)
+ tlb->end = address + PAGE_SIZE;
+}
+
+static inline void init_tlb_gather(struct mmu_gather *tlb)
+{
+ tlb->need_flush = 0;
+
+ tlb->start = TASK_SIZE;
+ tlb->end = 0;
+
+ if (tlb->fullmm) {
+ tlb->start = 0;
+ tlb->end = TASK_SIZE;
+ }
+}
+
+/* tlb_gather_mmu
+ * Return a pointer to an initialized struct mmu_gather.
+ */
+static inline struct mmu_gather *
+tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
+{
+ struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
+
+ tlb->mm = mm;
+ tlb->fullmm = full_mm_flush;
+
+ init_tlb_gather(tlb);
+
+ return tlb;
+}
+
+extern void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
+ unsigned long end);
+
+static inline void
+tlb_flush_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
+{
+ if (!tlb->need_flush)
+ return;
+
+ flush_tlb_mm_range(tlb->mm, tlb->start, tlb->end);
+ init_tlb_gather(tlb);
+}
+
+/* tlb_finish_mmu
+ * Called at the end of the shootdown operation to free up any resources
+ * that were required.
+ */
+static inline void
+tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
+{
+ tlb_flush_mmu(tlb, start, end);
+
+ /* keep the page table cache within bounds */
+ check_pgt_cache();
+
+ put_cpu_var(mmu_gathers);
+}
+
+/* tlb_remove_page
+ * Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)),
+ * while handling the additional races in SMP caused by other CPUs
+ * caching valid mappings in their TLBs.
+ */
+static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
+{
+ tlb->need_flush = 1;
+ free_page_and_swap_cache(page);
+ return;
+}
+
+/**
+ * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
+ *
+ * Record the fact that pte's were really umapped in ->need_flush, so we can
+ * later optimise away the tlb invalidate. This helps when userspace is
+ * unmapping already-unmapped pages, which happens quite a lot.
+ */
+#define tlb_remove_tlb_entry(tlb, ptep, address) \
+ do { \
+ tlb->need_flush = 1; \
+ __tlb_remove_tlb_entry(tlb, ptep, address); \
+ } while (0)
+
+#define pte_free_tlb(tlb, ptep) __pte_free_tlb(tlb, ptep)
+
+#define pud_free_tlb(tlb, pudp) __pud_free_tlb(tlb, pudp)
+
+#define pmd_free_tlb(tlb, pmdp) __pmd_free_tlb(tlb, pmdp)
+
+#define tlb_migrate_finish(mm) do {} while (0)
#endif
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH 1/6] UML - Customize tlb.h
2007-12-06 17:06 [PATCH 1/6] UML - Customize tlb.h Jeff Dike
@ 2007-12-06 19:46 ` Andrew Morton
2007-12-06 20:19 ` Jeff Dike
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2007-12-06 19:46 UTC (permalink / raw)
To: Jeff Dike; +Cc: linux-kernel, user-mode-linux-devel
On Thu, 6 Dec 2007 12:06:40 -0500
Jeff Dike <jdike@addtoit.com> wrote:
> Customize the hooks in tlb.h to optimize TLB flushing some more.
>
> Add start and end fields to tlb_gather_mmu, which are used to limit
> the address space range scanned when a region is unmapped.
>
> The interfaces which just free page tables, without actually changing
> mappings, don't need to cause a TLB flush.
>
> ...
>
> +void flush_tlb_mm(struct mm_struct *mm)
> +{
> + struct vm_area_struct *vma = mm->mmap;
> +
> + if (atomic_read(&mm->mm_users) == 0)
> + return;
Under which circumstances does this test succeed?
> + while (vma != NULL) {
> + fix_range(mm, vma->vm_start, vma->vm_end, 0);
> + vma = vma->vm_next;
> + }
> }
>
> void force_flush_all(void)
> Index: linux-2.6-git/include/asm-um/tlb.h
> ===================================================================
> --- linux-2.6-git.orig/include/asm-um/tlb.h 2007-12-06 10:34:31.000000000 -0500
> +++ linux-2.6-git/include/asm-um/tlb.h 2007-12-06 10:58:34.000000000 -0500
> @@ -1,6 +1,125 @@
> #ifndef __UM_TLB_H
> #define __UM_TLB_H
>
> -#include <asm/arch/tlb.h>
> +#include <linux/swap.h>
> +#include <asm/pgalloc.h>
> +#include <asm/tlbflush.h>
> +
> +#define tlb_start_vma(tlb, vma) do { } while (0)
> +#define tlb_end_vma(tlb, vma) do { } while (0)
> +#define tlb_flush(tlb) flush_tlb_mm((tlb)->mm)
> +
> +/* struct mmu_gather is an opaque type used by the mm code for passing around
> + * any data needed by arch specific code for tlb_remove_page.
> + */
> +struct mmu_gather {
> + struct mm_struct *mm;
> + unsigned int need_flush; /* Really unmapped some ptes? */
> + unsigned long start;
> + unsigned long end;
> + unsigned int fullmm; /* non-zero means full mm flush */
> +};
> +
> +/* Users of the generic TLB shootdown code must declare this storage space. */
> +DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
> +
> +static inline void __tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep,
> + unsigned long address)
> +{
> + if (tlb->start > address)
> + tlb->start = address;
> + if (tlb->end < address + PAGE_SIZE)
> + tlb->end = address + PAGE_SIZE;
> +}
> +
> +static inline void init_tlb_gather(struct mmu_gather *tlb)
> +{
> + tlb->need_flush = 0;
> +
> + tlb->start = TASK_SIZE;
> + tlb->end = 0;
> +
> + if (tlb->fullmm) {
> + tlb->start = 0;
> + tlb->end = TASK_SIZE;
> + }
> +}
> +
> +/* tlb_gather_mmu
> + * Return a pointer to an initialized struct mmu_gather.
> + */
> +static inline struct mmu_gather *
> +tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
> +{
> + struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
> +
> + tlb->mm = mm;
> + tlb->fullmm = full_mm_flush;
> +
> + init_tlb_gather(tlb);
> +
> + return tlb;
> +}
This file rather needs an inclusion of percpu.h. I guess you got lucky.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH 1/6] UML - Customize tlb.h
2007-12-06 19:46 ` Andrew Morton
@ 2007-12-06 20:19 ` Jeff Dike
0 siblings, 0 replies; 3+ messages in thread
From: Jeff Dike @ 2007-12-06 20:19 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-kernel, user-mode-linux-devel
On Thu, Dec 06, 2007 at 11:46:42AM -0800, Andrew Morton wrote:
> > +void flush_tlb_mm(struct mm_struct *mm)
> > +{
> > + struct vm_area_struct *vma = mm->mmap;
> > +
> > + if (atomic_read(&mm->mm_users) == 0)
> > + return;
>
> Under which circumstances does this test succeed?
Sigh, none. The other copy obviously succeeds during exit - this one
isn't needed.
> This file rather needs an inclusion of percpu.h. I guess you got
> lucky.
Yup, drop this, and I'll send a fixed version.
Jeff
--
Work email - jdike at linux dot intel dot com
^ permalink raw reply [flat|nested] 3+ messages in thread
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