x86/tlb: do flush_tlb_kernel_range by 'invlpg'

This patch do flush_tlb_kernel_range by 'invlpg'. The performance pay
and gain was analyzed in previous patch
(x86/flush_tlb: try flush_tlb_single one by one in flush_tlb_range).

In the testing: http://lkml.org/lkml/2012/6/21/10

The pay is mostly covered by long kernel path, but the gain is still
quite clear, memory access in user APP can increase 30+% when kernel
execute this funtion.

Signed-off-by: Alex Shi <alex.shi@intel.com>
Link: http://lkml.kernel.org/r/1340845344-27557-10-git-send-email-alex.shi@intel.com
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 2b5f506a7655..613cd83e8c0c 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -264,6 +264,36 @@ void flush_tlb_all(void)
         on_each_cpu(do_flush_tlb_all, NULL, 1);
 }
 
+static void do_kernel_range_flush(void *info)
+{
+        struct flush_tlb_info *f = info;
+        unsigned long addr;
+
+        /* flush range by one by one 'invlpg' */
+        for (addr = f->flush_start; addr < f->flush_end; addr += PAGE_SIZE)
+                __flush_tlb_single(addr);
+}
+
+void flush_tlb_kernel_range(unsigned long start, unsigned long end)
+{
+        unsigned act_entries;
+        struct flush_tlb_info info;
+
+        /* In modern CPU, last level tlb used for both data/ins */
+        act_entries = tlb_lld_4k[ENTRIES];
+
+        /* Balance as user space task's flush, a bit conservative */
+        if (end == TLB_FLUSH_ALL || tlb_flushall_shift == -1 ||
+                (end - start) >> PAGE_SHIFT > act_entries >> tlb_flushall_shift)
+
+                on_each_cpu(do_flush_tlb_all, NULL, 1);
+        else {
+                info.flush_start = start;
+                info.flush_end = end;
+                on_each_cpu(do_kernel_range_flush, &info, 1);
+        }
+}
+
 #ifdef CONFIG_DEBUG_TLBFLUSH
 static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
                              size_t count, loff_t *ppos)