From: Minchan Kim <minchan@kernel.org>
To: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
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: Fri, 12 Mar 2021 09:17:23 -0800 [thread overview]
Message-ID: <YEuiI44IRjBOQ8Wy@google.com> (raw)
In-Reply-To: <1527f16f-4376-a10d-4e72-041926cf38da@redhat.com>
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.
*/
next prev parent reply other threads:[~2021-03-12 17:18 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 [this message]
2021-03-16 18:26 ` Minchan Kim
2021-03-17 11:18 ` David Hildenbrand
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
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