Re: Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

It fixes the below issue.

1. Large size buffer allocation using cma_alloc successful with unevictable pages.

cma_alloc of current kernel will fail due to unevictable pages.

Solved the below issue of cma_alloc

-----------------------------------------------------------------------------------------------------------------------------------------
 [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
 [   24.726949] page->mem_cgroup:bd008c00
 [   24.730693] ------------[ cut here ]------------
 [   24.735304] kernel BUG at mm/vmscan.c:1350!
 [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
-----------------------------------------------------------------------------------------------------------------------------------------


From: Pankaj Suryawanshi
Sent: 15 March 2019 15:41:57
To: Kirill Tkhai; Michal Hocko; aneesh.kumar@xxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx; minchan@xxxxxxxxxx; linux-mm@xxxxxxxxx; khandual@xxxxxxxxxxxxxxxxxx; hillf.zj@xxxxxxxxxxxxxxx; vbabka@xxxxxxx
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



[ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]

From: Pankaj Suryawanshi
Sent: 15 March 2019 11:35:05
To: Kirill Tkhai; Michal Hocko
Cc: linux-kernel@xxxxxxxxxxxxxxx; minchan@xxxxxxxxxx; linux-mm@xxxxxxxxx
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



[ cc linux-mm ]


From: Pankaj Suryawanshi
Sent: 14 March 2019 19:14:40
To: Kirill Tkhai; Michal Hocko
Cc: linux-kernel@xxxxxxxxxxxxxxx; minchan@xxxxxxxxxx
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



Hello ,

Please ignore the curly braces, they are just for debugging.

Below is the updated patch.


diff --git a/mm/vmscan.c b/mm/vmscan.c
index be56e2e..12ac353 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                sc->nr_scanned++;

                if (unlikely(!page_evictable(page)))
-                       goto activate_locked;
+                      goto cull_mlocked;

                if (!sc->may_unmap && page_mapped(page))
                        goto keep_locked;
@@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                } else
                        list_add(&page->lru, &free_pages);
                continue;
-
+cull_mlocked:
+                if (PageSwapCache(page))
+                        try_to_free_swap(page);
+                unlock_page(page);
+                list_add(&page->lru, &ret_pages);
+                continue;
 activate_locked:
                /* Not a candidate for swapping, so reclaim swap space. */
                if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||



Regards,
Pankaj


From: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Sent: 14 March 2019 14:55:34
To: Pankaj Suryawanshi; Michal Hocko
Cc: linux-kernel@xxxxxxxxxxxxxxx; minchan@xxxxxxxxxx
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages


On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>
> I am using kernel version 4.14.65 (on Android pie [ARM]).
>
> No additional patches applied on top of vanilla.(Core MM).
>
> If  I change in the vmscan.c as below patch, it will work.

Sorry, but 4.14.65 does not have braces around trylock_page(),
like in your patch below.

See      https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65

[...]

>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index be56e2e..2e51edc 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                  page = lru_to_page(page_list);
>>                  list_del(&page->lru);
>>
>>                 if (!trylock_page(page)) {
>>                          goto keep;
>>                 }

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