Messages in this thread | | | From | Leon Romanovsky <> | Date | Mon, 15 Jun 2015 09:08:02 +0300 | Subject | Re: [RFC 2/3] mm: make optimistic check for swapin readahead |
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On Mon, Jun 15, 2015 at 8:43 AM, Rik van Riel <riel@redhat.com> wrote: > On 06/15/2015 01:40 AM, Leon Romanovsky wrote: >> On Sun, Jun 14, 2015 at 6:04 PM, Ebru Akagunduz >> <ebru.akagunduz@gmail.com> 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; >> Sorry for asking, my knoweldge of THP is very limited, but why did you >> choose this default value? >> From the discussion followed by your patch >> (https://lkml.org/lkml/2015/2/27/432), I got an impression that it is >> not necessary right value. > > I believe that Ebru's main focus for this initial version of > the patch series was to get the _mechanism_ (patch 3) right, > while having a fairly simple policy to drive it. > > Any suggestions on when it is a good idea to bring in pages > from swap, and whether to treat resident-in-swap-cache pages > differently from need-to-be-paged-in pages, and what other > factors should be examined, are very welcome... My concern with these patches that they deal with specific load/scenario (most of the application returned back from swap). In scenario there only 10% of data will be required, it theoretically can bring upto 80% data (70% waste).
> > -- > All rights reversed
-- Leon Romanovsky | Independent Linux Consultant www.leon.nu | leon@leon.nu
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