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    Subject[PATCH v8 8/8] x86/tlb: do flush_tlb_kernel_range by 'invlpg'
    Date
    This patch do flush_tlb_kernel_range by 'invlpg'. The performance pay
    and gain was analyzed in my patch (x86/flush_tlb: try flush_tlb_single
    one by one in flush_tlb_range). Now we move this logical into kernel
    part. The pay is multiple 'invlpg' execution cost, that is same. but
    the gain(cost reducing of TLB entries refilling) is absoulutely
    increased.

    Signed-off-by: Alex Shi <alex.shi@intel.com>
    ---
    arch/x86/include/asm/tlbflush.h | 13 +++++++------
    arch/x86/mm/tlb.c | 30 ++++++++++++++++++++++++++++++
    2 files changed, 37 insertions(+), 6 deletions(-)

    diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
    index 008043d..f434842 100644
    --- a/arch/x86/include/asm/tlbflush.h
    +++ b/arch/x86/include/asm/tlbflush.h
    @@ -123,6 +123,12 @@ static inline void reset_lazy_tlbstate(void)
    {
    }

    +static inline void flush_tlb_kernel_range(unsigned long start,
    + unsigned long end)
    +{
    + flush_tlb_all();
    +}
    +
    #else /* SMP */

    #include <asm/smp.h>
    @@ -139,6 +145,7 @@ extern void flush_tlb_current_task(void);
    extern void flush_tlb_page(struct vm_area_struct *, unsigned long);
    extern void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
    unsigned long end, unsigned long vmflag);
    +extern void flush_tlb_kernel_range(unsigned long start, unsigned long end);

    #define flush_tlb() flush_tlb_current_task()

    @@ -168,10 +175,4 @@ static inline void reset_lazy_tlbstate(void)
    native_flush_tlb_others(mask, mm, start, end)
    #endif

    -static inline void flush_tlb_kernel_range(unsigned long start,
    - unsigned long end)
    -{
    - flush_tlb_all();
    -}
    -
    #endif /* _ASM_X86_TLBFLUSH_H */
    diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
    index 2b5f506..fa78df9 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];
    +
    + /* tlb_flushall_shift is on balance point, details in commit log */
    + 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)
    --
    1.7.5.4


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