Re: [RFC 2/3] mm: make optimistic check for swapin readahead

[Leon Romanovsky <leon@leon.nu>]

On Mon, Jun 15, 2015 at 5:05 PM, Rik van Riel <riel@redhat.com> wrote:
>
> On 06/14/2015 11:04 AM, Ebru Akagunduz wrote:
> > This patch makes optimistic check for swapin readahead
> > to increase thp collapse rate. Before getting swapped
> > out pages to memory, checks them and allows up to a
> > certain number. It also prints out using tracepoints
> > amount of unmapped ptes.
> >
> > Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>
>
> > @@ -2639,11 +2640,11 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
> >  {
> >       pmd_t *pmd;
> >       pte_t *pte, *_pte;
> > -     int ret = 0, none_or_zero = 0;
> > +     int ret = 0, none_or_zero = 0, unmapped = 0;
> >       struct page *page;
> >       unsigned long _address;
> >       spinlock_t *ptl;
> > -     int node = NUMA_NO_NODE;
> > +     int node = NUMA_NO_NODE, max_ptes_swap = HPAGE_PMD_NR/8;
> >       bool writable = false, referenced = false;
>
> This has the effect of only swapping in 4kB pages to form a THP
> if 7/8th of the THP is already resident in memory.
Thanks for clarifing it to me.

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