From: Pankaj Suryawanshi <pankajssuryawanshi@gmail.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kernelnewbies@kernelnewbies.org, vbabka@suse.cz,
mhocko@kernel.org, minchan@kernel.org
Subject: vmscan.c: Reclaim unevictable pages.
Date: Sat, 6 Apr 2019 11:29:27 +0530 [thread overview]
Message-ID: <CACDBo57pEVRjOBf0yLMQ+KuGPeOuFcMufGVzjPJVnwfLFjzFSA@mail.gmail.com> (raw)
Hello ,
shrink_page_list() returns , number of pages reclaimed, when pages is
unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) ||
PageUnevicatble(page),page);
We can add the unevictable pages in reclaim list in
shrink_page_list(), return total number of reclaim pages including
unevictable pages, let the caller handle unevictable pages.
I think the problem is shrink_page_list is awkard. If page is
unevictable it goto activate_locked->keep_locked->keep lables, keep
lable list_add the unevictable pages and throw the VM_BUG instead of
passing it to caller while it relies on caller for
non-reclaimed-non-unevictable page's putback.
I think we can make it consistent so that shrink_page_list could
return non-reclaimed pages via page_list and caller can handle it. As
an advance, it could try to migrate mlocked pages without retrial.
Below is the issue i observed of CMA_ALLOC of large size buffer :
(Kernel version - 4.14.65 With Android Pie.
[ 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
Below is the patch which solved this issue :
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) ||
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 page
Please let me know if anything i am missing.
Regards,
Pankaj
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
next reply other threads:[~2019-04-08 0:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-06 5:59 Pankaj Suryawanshi [this message]
2019-04-17 11:39 ` vmscan.c: Reclaim unevictable pages Vlastimil Babka
2019-04-28 12:38 ` Pankaj Suryawanshi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CACDBo57pEVRjOBf0yLMQ+KuGPeOuFcMufGVzjPJVnwfLFjzFSA@mail.gmail.com \
--to=pankajssuryawanshi@gmail.com \
--cc=kernelnewbies@kernelnewbies.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=minchan@kernel.org \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).