On 06/15/2015 02:08 AM, Leon Romanovsky wrote:
> On Mon, Jun 15, 2015 at 8:43 AM, Rik van Riel <r...@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.akagun...@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.akagun...@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).
The chosen threshold ensures that the remaining non-resident
4kB pages in a THP are only brought in if 7/8th (or 87.5%) of
the pages are already resident.
--
All rights reversed
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
