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From: David Howells <dhowells@redhat.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: dhowells@redhat.com,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-cachefs@redhat.com,
	linux-afs@lists.infradead.org
Subject: Re: [PATCH v5 00/27] Memory Folios
Date: Tue, 23 Mar 2021 17:50:31 +0000	[thread overview]
Message-ID: <2749829.1616521831@warthog.procyon.org.uk> (raw)
In-Reply-To: <YFja/LRC1NI6quL6@cmpxchg.org>

Johannes Weiner <hannes@cmpxchg.org> wrote:

> So I fully agree with the motivation behind this patch. But I do
> wonder why it's special-casing the commmon case instead of the rare
> case. It comes at a huge cost. Short term, the churn of replacing
> 'page' with 'folio' in pretty much all instances is enormous.
> 
> And longer term, I'm not convinced folio is the abstraction we want
> throughout the kernel. If nobody should be dealing with tail pages in
> the first place, why are we making everybody think in 'folios'? Why
> does a filesystem care that huge pages are composed of multiple base
> pages internally? This feels like an implementation detail leaking out
> of the MM code. The vast majority of places should be thinking 'page'
> with a size of 'page_size()'. Including most parts of the MM itself.

I like the idea of logically separating individual hardware pages from
abstract bundles of pages by using a separate type for them - at least in
filesystem code.  I'm trying to abstract some of the handling out of the
network filesystems and into a common library plus ITER_XARRAY to insulate
those filesystems from the VM.

David



      parent reply	other threads:[~2021-03-23 17:51 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-20  5:40 [PATCH v5 00/27] Memory Folios Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 01/27] fs/cachefiles: Remove wait_bit_key layout dependency Matthew Wilcox (Oracle)
2021-03-22  8:06   ` Christoph Hellwig
2021-03-20  5:40 ` [PATCH v5 02/27] mm/writeback: Add wait_on_page_writeback_killable Matthew Wilcox (Oracle)
2021-03-22  8:07   ` Christoph Hellwig
2021-03-20  5:40 ` [PATCH v5 03/27] afs: Use wait_on_page_writeback_killable Matthew Wilcox (Oracle)
2021-03-22  8:08   ` Christoph Hellwig
2021-03-20  5:40 ` [PATCH v5 04/27] mm: Introduce struct folio Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 05/27] mm: Add folio_pgdat and folio_zone Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 06/27] mm/vmstat: Add functions to account folio statistics Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 07/27] mm/debug: Add VM_BUG_ON_FOLIO and VM_WARN_ON_ONCE_FOLIO Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 08/27] mm: Add put_folio Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 09/27] mm: Add get_folio Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 10/27] mm: Create FolioFlags Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 11/27] mm: Handle per-folio private data Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 12/27] mm: Add folio_index, folio_file_page and folio_contains Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 13/27] mm/util: Add folio_mapping and folio_file_mapping Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 14/27] mm/memcg: Add folio wrappers for various functions Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 15/27] mm/filemap: Add unlock_folio Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 16/27] mm/filemap: Add lock_folio Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 17/27] mm/filemap: Add lock_folio_killable Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 18/27] mm/filemap: Add __lock_folio_async Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 19/27] mm/filemap: Add __lock_folio_or_retry Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 20/27] mm/filemap: Add wait_on_folio_locked Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 21/27] mm/filemap: Add end_folio_writeback Matthew Wilcox (Oracle)
2021-03-20  5:40 ` [PATCH v5 22/27] mm/writeback: Add wait_on_folio_writeback Matthew Wilcox (Oracle)
2021-03-20  5:41 ` [PATCH v5 23/27] mm/writeback: Add wait_for_stable_folio Matthew Wilcox (Oracle)
2021-03-20  5:41 ` [PATCH v5 24/27] mm/filemap: Convert wait_on_page_bit to wait_on_folio_bit Matthew Wilcox (Oracle)
2021-03-21  7:10   ` kernel test robot
2021-03-20  5:41 ` [PATCH v5 25/27] mm/filemap: Convert wake_up_page_bit to wake_up_folio_bit Matthew Wilcox (Oracle)
2021-03-20  5:41 ` [PATCH v5 26/27] mm/filemap: Convert page wait queues to be folios Matthew Wilcox (Oracle)
2021-03-20  7:54   ` kernel test robot
2021-03-20  5:41 ` [PATCH v5 27/27] mm/doc: Build kerneldoc for various mm files Matthew Wilcox (Oracle)
2021-03-22  3:25 ` [PATCH v5 00/27] Memory Folios Matthew Wilcox
2021-03-22  9:25 ` [PATCH v5 01/27] fs/cachefiles: Remove wait_bit_key layout dependency David Howells
2021-03-22  9:26 ` [PATCH v5 02/27] mm/writeback: Add wait_on_page_writeback_killable David Howells
2021-03-22  9:27 ` [PATCH v5 03/27] afs: Use wait_on_page_writeback_killable David Howells
2021-03-22 19:41   ` Matthew Wilcox
2021-03-22 17:59 ` [PATCH v5 00/27] Memory Folios Johannes Weiner
2021-03-22 18:47   ` Matthew Wilcox
2021-03-24  0:29     ` Johannes Weiner
2021-03-24  6:24       ` Matthew Wilcox
2021-03-26 17:48         ` Johannes Weiner
2021-03-29 16:58           ` Matthew Wilcox
2021-03-29 17:56             ` Matthew Wilcox
2021-03-30 19:30             ` Johannes Weiner
2021-03-30 21:09               ` Matthew Wilcox
2021-03-31 18:14                 ` Johannes Weiner
2021-03-31 18:28                   ` Matthew Wilcox
2021-04-01  5:05                 ` Al Viro
2021-04-01 12:07                   ` Matthew Wilcox
2021-04-01 16:00                   ` Johannes Weiner
2021-03-31 14:54               ` Christoph Hellwig
2021-03-23 15:50   ` Christoph Hellwig
2021-03-23 11:29 ` [PATCH v5 03/27] afs: Use wait_on_page_writeback_killable David Howells
2021-03-23 17:50 ` David Howells [this message]

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