lkml.org 
[lkml]   [2009]   [Mar]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH 1/2] mm: tlb: Add range to tlb_start_vma() and tlb_end_vma()
On Mon, 9 Mar 2009, Aaro Koskinen wrote:
> Hugh Dickins wrote:
>
> > I don't see that you need to change the interface and other arches
> > at all. What prevents ARM from noting the first and last addresses
> > freed in its struct mmu_gather when tlb_remove_tlb_entry() is called
> > (see arch/um/include/asm/tlb.h for an example of that), then using
> > that in its tlb_end_vma() TLB flushing?
>
> This would probably work, thanks for pointing it out. I should have taken a
> better look of the full API, not just what was implemented in ARM.
>
> So, there's a new ARM-only patch draft below based on this idea, adding also
> linux-arm-kernel again.

This one is much better, thank you. I would think it more natural
to do the initialization of range_start and range_end in your
tlb_start_vma() - to complement tlb_end_vma() where you deal with
the final result - rather than in two places you have sited it;
but that's somewhat a matter of taste, your patch should work as is.

Hugh

>
> ---
>
> From: Aaro Koskinen <Aaro.Koskinen@nokia.com>
> Subject: [RFC PATCH] [ARM] Flush only the needed range when unmapping VMA
>
> Signed-off-by: Aaro Koskinen <Aaro.Koskinen@nokia.com>
> ---
> arch/arm/include/asm/tlb.h | 25 ++++++++++++++++++++++---
> 1 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
> index 857f1df..2729fb9 100644
> --- a/arch/arm/include/asm/tlb.h
> +++ b/arch/arm/include/asm/tlb.h
> @@ -36,6 +36,8 @@
> struct mmu_gather {
> struct mm_struct *mm;
> unsigned int fullmm;
> + unsigned long range_start;
> + unsigned long range_end;
> };
>
> DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
> @@ -47,6 +49,8 @@ tlb_gather_mmu(struct mm_struct *mm, unsigned int
> full_mm_flush)
>
> tlb->mm = mm;
> tlb->fullmm = full_mm_flush;
> + tlb->range_start = TASK_SIZE;
> + tlb->range_end = 0;
>
> return tlb;
> }
> @@ -63,7 +67,19 @@ tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start,
> unsigned long end)
> put_cpu_var(mmu_gathers);
> }
>
> -#define tlb_remove_tlb_entry(tlb,ptep,address) do { } while (0)
> +/*
> + * Memorize the range for the TLB flush.
> + */
> +static inline void
> +tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep, unsigned long addr)
> +{
> + if (!tlb->fullmm) {
> + if (addr < tlb->range_start)
> + tlb->range_start = addr;
> + if (addr + PAGE_SIZE > tlb->range_end)
> + tlb->range_end = addr + PAGE_SIZE;
> + }
> +}
>
> /*
> * In the case of tlb vma handling, we can optimise these away in the
> @@ -80,8 +96,11 @@ tlb_start_vma(struct mmu_gather *tlb, struct vm_area_struct
> *vma)
> static inline void
> tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
> {
> - if (!tlb->fullmm)
> - flush_tlb_range(vma, vma->vm_start, vma->vm_end);
> + if (!tlb->fullmm && tlb->range_end > 0) {
> + flush_tlb_range(vma, tlb->range_start, tlb->range_end);
> + tlb->range_start = TASK_SIZE;
> + tlb->range_end = 0;
> + }
> }
>
> #define tlb_remove_page(tlb,page) free_page_and_swap_cache(page)
> --
> 1.5.4.3


\
 
 \ /
  Last update: 2009-03-09 19:25    [W:0.052 / U:3.404 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site