From: David Hildenbrand <david@redhat.com>
To: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
joaodias@google.com, surenb@google.com, cgoldswo@codeaurora.org,
willy@infradead.org, mhocko@suse.com, vbabka@suse.cz,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v3 3/3] mm: fs: Invalidate BH LRU during page migration
Date: Wed, 17 Mar 2021 12:18:07 +0100 [thread overview]
Message-ID: <239b45ff-dad0-6cd0-4f6e-18159185cd6d@redhat.com> (raw)
In-Reply-To: <YFD4cz6+0U2jgTzH@google.com>
On 16.03.21 19:26, Minchan Kim wrote:
> On Fri, Mar 12, 2021 at 09:17:23AM -0800, Minchan Kim wrote:
>> On Fri, Mar 12, 2021 at 10:33:48AM +0100, David Hildenbrand wrote:
>>> On 12.03.21 10:03, David Hildenbrand wrote:
>>>> On 10.03.21 17:14, Minchan Kim wrote:
>>>>> ffer_head LRU caches will be pinned and thus cannot be migrated.
>>>>> This can prevent CMA allocations from succeeding, which are often used
>>>>> on platforms with co-processors (such as a DSP) that can only use
>>>>> physically contiguous memory. It can also prevent memory
>>>>> hot-unplugging from succeeding, which involves migrating at least
>>>>> MIN_MEMORY_BLOCK_SIZE bytes of memory, which ranges from 8 MiB to 1
>>>>> GiB based on the architecture in use.
>>>>
>>>> Actually, it's memory_block_size_bytes(), which can be even bigger
>>>> (IIRC, 128MiB..2 GiB on x86-64) that fails to get offlined. But that
>>>> will prevent bigger granularity (e.g., a whole DIMM) from getting unplugged.
>>>>
>>>>>
>>>>> Correspondingly, invalidate the BH LRU caches before a migration
>>>>> starts and stop any buffer_head from being cached in the LRU caches,
>>>>> until migration has finished.
>>>>
>>>> Sounds sane to me.
>>>>
>>>
>>> Diving a bit into the code, I am wondering:
>>>
>>>
>>> a) Are these buffer head pages marked as movable?
>>>
>>> IOW, are they either PageLRU() or __PageMovable()?
>>>
>>>
>>> b) How do these pages end up on ZONE_MOVABLE or MIGRATE_CMA?
>>>
>>> I assume these pages come via
>>> alloc_page_buffers()->alloc_buffer_head()->kmem_cache_zalloc(GFP_NOFS |
>>> __GFP_ACCOUNT)
>>>
>>
>> It's indirect it was not clear
>>
>> try_to_release_page
>> try_to_free_buffers
>> buffer_busy
>> failed
>>
>> Yeah, comment is misleading. This one would be better.
>>
>> /*
>> * the refcount of buffer_head in bh_lru prevents dropping the
>> * attached page(i.e., try_to_free_buffers) so it could cause
>> * failing page migrationn.
>> * Skip putting upcoming bh into bh_lru until migration is done.
>> */
>
Thanks, that makes more sense to me now :)
> Hi Andrew,
>
> Could you fold this comment fix patch? If you prefer formal patch,
> let me know. I will resend it.
>
> Thank you.
>
> From 0774f21e2dc8220fc2be80c25f711cb061363519 Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@kernel.org>
> Date: Fri, 12 Mar 2021 09:17:34 -0800
> Subject: [PATCH] comment fix
>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> fs/buffer.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index ca9dd736bcb8..8602dcbe0327 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -1265,8 +1265,9 @@ static void bh_lru_install(struct buffer_head *bh)
>
> check_irqs_on();
> /*
> - * buffer_head in bh_lru could increase refcount of the page
> - * until it will be invalidated. It causes page migraion failure.
> + * the refcount of buffer_head in bh_lru prevents dropping the
> + * attached page(i.e., try_to_free_buffers) so it could cause
> + * failing page migratoin.
s/migratoin/migration/
> * Skip putting upcoming bh into bh_lru until migration is done.
> */
> if (lru_cache_disabled())
>
Acked-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-03-17 11:19 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-10 16:14 [PATCH v3 1/3] mm: replace migrate_prep with lru_add_drain_all Minchan Kim
2021-03-10 16:14 ` [PATCH v3 2/3] mm: disable LRU pagevec during the migration temporarily Minchan Kim
2021-03-11 22:41 ` Chris Goldsworthy
2021-03-14 5:10 ` Chris Goldsworthy
2021-03-12 8:21 ` Michal Hocko
2021-03-12 9:00 ` David Hildenbrand
2021-03-18 0:13 ` Andrew Morton
2021-03-18 1:13 ` Minchan Kim
2021-03-18 8:09 ` Michal Hocko
2021-03-10 16:14 ` [PATCH v3 3/3] mm: fs: Invalidate BH LRU during page migration Minchan Kim
2021-03-12 9:03 ` David Hildenbrand
2021-03-12 9:33 ` David Hildenbrand
2021-03-12 17:17 ` Minchan Kim
2021-03-16 18:26 ` Minchan Kim
2021-03-17 11:18 ` David Hildenbrand [this message]
2021-03-17 2:37 ` [mm] 8fd8d23ab1: WARNING:at_fs/buffer.c:#__brelse kernel test robot
2021-03-17 16:29 ` Minchan Kim
2021-03-19 14:05 ` Oliver Sang
2021-03-19 16:47 ` Minchan Kim
2021-03-12 8:19 ` [PATCH v3 1/3] mm: replace migrate_prep with lru_add_drain_all Michal Hocko
2021-03-12 8:53 ` David Hildenbrand
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=239b45ff-dad0-6cd0-4f6e-18159185cd6d@redhat.com \
--to=david@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=cgoldswo@codeaurora.org \
--cc=joaodias@google.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=minchan@kernel.org \
--cc=surenb@google.com \
--cc=vbabka@suse.cz \
--cc=willy@infradead.org \
/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).