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Message-ID: <AANLkTinx6wBUxQKWeCfcLbqB60qvTFWd8EHS0cGTj-Ma@mail.gmail.com>
Date: Wed, 8 Dec 2010 16:55:11 +0900
From: Minchan Kim <minchan.kim@...il.com>
To: Hugh Dickins <hughd@...gle.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 Wed, Dec 8, 2010 at 4:26 PM, Hugh Dickins <hughd@...gle.com> wrote:
> 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.
That encourages me(But I don't mean I will use attachment again. :)).
>
>>
>> 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);
>
>
Much clean.
>> 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?
It has done very careless. Sorry for that. I thought i_mmap_lock
always is used with check_mapping. Clear wrong!
My concern is that if we don't have such routine, caller use only
ingore_reference should initialize i_mmap_lock with NULL.
It's bad.
Hmm...
>
> Hugh
>
--
Kind regards,
Minchan Kim
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