Thread (34 messages) 34 messages, 7 authors, 2012-06-29

Re: [PATCH 3/3] x86: add local_tlb_flush_kernel_range()

From: Konrad Rzeszutek Wilk <hidden>
Date: 2012-06-25 23:01:29
Also in: lkml

On Mon, Jun 25, 2012 at 12:14 PM, Seth Jennings
[off-list ref] wrote:
This patch adds support for a local_tlb_flush_kernel_range()
function for the x86 arch.  This function allows for CPU-local
TLB flushing, potentially using invlpg for single entry flushing,
using an arch independent function name.
What x86 hardware did you use to figure the optimal number?
quoted hunk ↗ jump to hunk
Signed-off-by: Seth Jennings <redacted>
---
 arch/x86/include/asm/tlbflush.h |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 36a1a2a..92a280b 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -168,4 +168,25 @@ static inline void flush_tlb_kernel_range(unsigned long start,
       flush_tlb_all();
 }

+#define __HAVE_LOCAL_FLUSH_TLB_KERNEL_RANGE
+/*
+ * INVLPG_BREAK_EVEN_PAGES is the number of pages after which single tlb
+ * flushing becomes more costly than just doing a complete tlb flush.
+ * While this break even point varies among x86 hardware, tests have shown
+ * that 8 is a good generic value.
+*/
+#define INVLPG_BREAK_EVEN_PAGES 8
+static inline void local_flush_tlb_kernel_range(unsigned long start,
+               unsigned long end)
+{
+       if (cpu_has_invlpg &&
+               (end - start)/PAGE_SIZE <= INVLPG_BREAK_EVEN_PAGES) {
+               while (start < end) {
+                       __flush_tlb_single(start);
+                       start += PAGE_SIZE;
+               }
+       } else
+               local_flush_tlb();
+}
+
 #endif /* _ASM_X86_TLBFLUSH_H */
--
1.7.9.5

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