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Subject[PATCH 3/3] arm64, mm: Use IPIs for TLB invalidation.
Date
From: David Daney <david.daney@cavium.com>

Most broadcast TLB invalidations are unnecessary. So when
invalidating for a given mm/vma target the only the needed CPUs via
and IPI.

For global TLB invalidations, also use IPI.

Tested on Cavium ThunderX.

This change reduces 'time make -j48' on kernel from 139s to 116s (83%
as long).

The patch is needed because of a ThunderX Pass1 erratum: Exclusive
store operations unreliable in the presence of broadcast TLB
invalidations. The performance improvements shown make it compelling
even without the erratum workaround need.

Signed-off-by: David Daney <david.daney@cavium.com>
---
arch/arm64/include/asm/tlbflush.h | 67 ++++++---------------------------------
arch/arm64/mm/flush.c | 46 +++++++++++++++++++++++++++
2 files changed, 56 insertions(+), 57 deletions(-)

diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
index 42c09ec..2c132b0 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -63,46 +63,22 @@
* only require the D-TLB to be invalidated.
* - kaddr - Kernel virtual memory address
*/
-static inline void flush_tlb_all(void)
-{
- dsb(ishst);
- asm("tlbi vmalle1is");
- dsb(ish);
- isb();
-}
-
-static inline void flush_tlb_mm(struct mm_struct *mm)
-{
- unsigned long asid = (unsigned long)ASID(mm) << 48;
+void flush_tlb_all(void);

- dsb(ishst);
- asm("tlbi aside1is, %0" : : "r" (asid));
- dsb(ish);
-}
+void flush_tlb_mm(struct mm_struct *mm);

static inline void flush_tlb_page(struct vm_area_struct *vma,
unsigned long uaddr)
{
- unsigned long addr = uaddr >> 12 |
- ((unsigned long)ASID(vma->vm_mm) << 48);
-
- dsb(ishst);
- asm("tlbi vae1is, %0" : : "r" (addr));
- dsb(ish);
+ /* Simplify to entire mm. */
+ flush_tlb_mm(vma->vm_mm);
}

static inline void __flush_tlb_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
- unsigned long asid = (unsigned long)ASID(vma->vm_mm) << 48;
- unsigned long addr;
- start = asid | (start >> 12);
- end = asid | (end >> 12);
-
- dsb(ishst);
- for (addr = start; addr < end; addr += 1 << (PAGE_SHIFT - 12))
- asm("tlbi vae1is, %0" : : "r"(addr));
- dsb(ish);
+ /* Simplify to entire mm. */
+ flush_tlb_mm(vma->vm_mm);
}

static inline void flush_tlb_all_local(void)
@@ -112,40 +88,17 @@ static inline void flush_tlb_all_local(void)
isb();
}

-static inline void __flush_tlb_kernel_range(unsigned long start, unsigned long end)
-{
- unsigned long addr;
- start >>= 12;
- end >>= 12;
-
- dsb(ishst);
- for (addr = start; addr < end; addr += 1 << (PAGE_SHIFT - 12))
- asm("tlbi vaae1is, %0" : : "r"(addr));
- dsb(ish);
- isb();
-}
-
-/*
- * This is meant to avoid soft lock-ups on large TLB flushing ranges and not
- * necessarily a performance improvement.
- */
-#define MAX_TLB_RANGE (1024UL << PAGE_SHIFT)
-
static inline void flush_tlb_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
- if ((end - start) <= MAX_TLB_RANGE)
- __flush_tlb_range(vma, start, end);
- else
- flush_tlb_mm(vma->vm_mm);
+ /* Simplify to entire mm. */
+ flush_tlb_mm(vma->vm_mm);
}

static inline void flush_tlb_kernel_range(unsigned long start, unsigned long end)
{
- if ((end - start) <= MAX_TLB_RANGE)
- __flush_tlb_kernel_range(start, end);
- else
- flush_tlb_all();
+ /* Simplify to all. */
+ flush_tlb_all();
}

/*
diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
index 4dfa397..45f24d3 100644
--- a/arch/arm64/mm/flush.c
+++ b/arch/arm64/mm/flush.c
@@ -20,6 +20,7 @@
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
+#include <linux/smp.h>

#include <asm/cacheflush.h>
#include <asm/cachetype.h>
@@ -27,6 +28,51 @@

#include "mm.h"

+static void flush_tlb_local(void *info)
+{
+ asm volatile("\n"
+ " tlbi vmalle1\n"
+ " isb sy"
+ );
+}
+
+static void flush_tlb_mm_local(void *info)
+{
+ unsigned long asid = (unsigned long)info;
+
+ asm volatile("\n"
+ " tlbi aside1, %0\n"
+ " isb sy"
+ : : "r" (asid)
+ );
+}
+
+void flush_tlb_all(void)
+{
+ /* Make sure page table modifications are visible. */
+ dsb(ishst);
+ /* IPI to all CPUs to do local flush. */
+ on_each_cpu(flush_tlb_local, NULL, 1);
+
+}
+EXPORT_SYMBOL(flush_tlb_all);
+
+void flush_tlb_mm(struct mm_struct *mm)
+{
+ if (!mm) {
+ flush_tlb_all();
+ } else {
+ unsigned long asid = (unsigned long)ASID(mm) << 48;
+ /* Make sure page table modifications are visible. */
+ dsb(ishst);
+ /* IPI to all CPUs to do local flush. */
+ on_each_cpu_mask(mm_cpumask(mm),
+ flush_tlb_mm_local, (void *)asid, 1);
+ }
+
+}
+EXPORT_SYMBOL(flush_tlb_mm);
+
void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
unsigned long end)
{
--
1.9.1


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