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Date: Tue, 7 Dec 2010 23:26:04 -0800 (PST)
From: Hugh Dickins <hughd@...gle.com>
To: Minchan Kim <minchan.kim@...il.com>
cc: Andrew Morton <akpm@...ux-foundation.org>,
Rik van Riel <riel@...hat.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
Johannes Weiner <hannes@...xchg.org>,
Nick Piggin <npiggin@...nel.dk>, Mel Gorman <mel@....ul.ie>,
Wu Fengguang <fengguang.wu@...el.com>
Subject: Re: [PATCH v4 7/7] Prevent activation of page in madvise_dontneed
On Tue, 7 Dec 2010, Minchan Kim wrote:
>
> How about this? Although it doesn't remove null dependency, it meet my
> goal without big overhead.
> It's just quick patch.
Roughly, yes; by "just quick patch" I take you to mean that I should
not waste time on all the minor carelessnesses scattered through it.
> If you agree, I will resend this version as formal patch.
> (If you suffered from seeing below word-wrapped source, see the
> attachment. I asked to google two time to support text-plain mode in
> gmail web but I can't receive any response until now. ;(. Lots of
> kernel developer in google. Please support this mode for us who can't
> use SMTP although it's a very small VOC)
Tiresome. Seems not to be high on gmail's priorities.
It's sad to see even Linus attaching patches these days.
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index e097df6..14ae918 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -771,6 +771,7 @@ struct zap_details {
> pgoff_t last_index; /* Highest page->index
> to unmap */
> spinlock_t *i_mmap_lock; /* For unmap_mapping_range: */
> unsigned long truncate_count; /* Compare vm_truncate_count */
> + int ignore_reference;
> };
>
> struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 319528b..fdb0253 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -162,18 +162,22 @@ static long madvise_dontneed(struct vm_area_struct * vma,
> struct vm_area_struct ** prev,
> unsigned long start, unsigned long end)
> {
> + struct zap_details details ;
> +
> *prev = vma;
> if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
> return -EINVAL;
>
> if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
> - struct zap_details details = {
> - .nonlinear_vma = vma,
> - .last_index = ULONG_MAX,
> - };
> - zap_page_range(vma, start, end - start, &details);
> - } else
> - zap_page_range(vma, start, end - start, NULL);
> + details.nonlinear_vma = vma;
> + details.last_index = ULONG_MAX;
> + } else {
> + details.nonlinear_vma = NULL;
> + details.last_index = NULL;
> + }
> +
> + details.ignore_references = true;
> + zap_page_range(vma, start, end - start, &details);
> return 0;
> }
>
> diff --git a/mm/memory.c b/mm/memory.c
> index ebfeedf..d46ac42 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -897,9 +897,15 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> pte_t *pte;
> spinlock_t *ptl;
> int rss[NR_MM_COUNTERS];
> -
> + bool ignore_reference = false;
> init_rss_vec(rss);
>
> + if (details && ((!details->check_mapping && !details->nonlinear_vma)
> + || !details->ignore_reference))
> + details = NULL;
> +
bool mark_accessed = true;
if (VM_SequentialReadHint(vma) ||
(details && details->ignore_reference))
mark_accessed = false;
if (details && !details->check_mapping && !details->nonlinear_vma)
details = NULL;
> pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
> arch_enter_lazy_mmu_mode();
> do {
> @@ -949,7 +955,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> if (pte_dirty(ptent))
> set_page_dirty(page);
> if (pte_young(ptent) &&
> - likely(!VM_SequentialReadHint(vma)))
> + likely(!VM_SequentialReadHint(vma)) &&
> + likely(!ignore_reference))
> mark_page_accessed(page);
if (pte_young(ptent) && mark_accessed)
mark_page_accessed(page);
> rss[MM_FILEPAGES]--;
> }
> @@ -1038,8 +1045,6 @@ static unsigned long unmap_page_range(struct
> mmu_gather *tlb,
> pgd_t *pgd;
> unsigned long next;
>
> - if (details && !details->check_mapping && !details->nonlinear_vma)
> - details = NULL;
>
> BUG_ON(addr >= end);
> mem_cgroup_uncharge_start();
> @@ -1102,7 +1107,8 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp,
> unsigned long tlb_start = 0; /* For tlb_finish_mmu */
> int tlb_start_valid = 0;
> unsigned long start = start_addr;
> - spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
> + spinlock_t *i_mmap_lock = details ?
> + (detais->check_mapping ? details->i_mmap_lock: NULL) : NULL;
Why that change?
Hugh
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