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Groups > linux.kernel > #1165029 > unrolled thread
| Started by | Rik van Riel <riel@redhat.com> |
|---|---|
| First post | 2015-06-15 07:50 +0200 |
| Last post | 2015-06-15 08:40 +0200 |
| Articles | 3 — 2 participants |
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Re: [RFC 2/3] mm: make optimistic check for swapin readahead Rik van Riel <riel@redhat.com> - 2015-06-15 07:50 +0200
Re: [RFC 2/3] mm: make optimistic check for swapin readahead Leon Romanovsky <leon@leon.nu> - 2015-06-15 08:10 +0200
Re: [RFC 2/3] mm: make optimistic check for swapin readahead Rik van Riel <riel@redhat.com> - 2015-06-15 08:40 +0200
| From | Rik van Riel <riel@redhat.com> |
|---|---|
| Date | 2015-06-15 07:50 +0200 |
| Subject | Re: [RFC 2/3] mm: make optimistic check for swapin readahead |
| Message-ID | <pBvrs-2G5-5@gated-at.bofh.it> |
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...
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| From | Leon Romanovsky <leon@leon.nu> |
|---|---|
| Date | 2015-06-15 08:10 +0200 |
| Message-ID | <pBvKN-3hf-7@gated-at.bofh.it> |
| In reply to | #1165029 |
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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| From | Rik van Riel <riel@redhat.com> |
|---|---|
| Date | 2015-06-15 08:40 +0200 |
| Message-ID | <pBwdP-3OT-3@gated-at.bofh.it> |
| In reply to | #1165039 |
On 06/15/2015 02:08 AM, Leon Romanovsky wrote:
> 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).
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.
--
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--
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Please read the FAQ at http://www.tux.org/lkml/
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