From: Matthew Wilcox <willy@infradead.org>
To: Yu Zhao <yuzhao@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
vbabka@suse.cz, alex.shi@linux.alibaba.com, guro@fb.com,
hannes@cmpxchg.org, hughd@google.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
mhocko@kernel.org, vdavydov.dev@gmail.com
Subject: Re: [PATCH] mm: test page->flags directly in page_lru()
Date: Thu, 25 Feb 2021 03:55:53 +0000 [thread overview]
Message-ID: <20210225035553.GX2858050@casper.infradead.org> (raw)
In-Reply-To: <YDbmT87E106uS1Xa@google.com>
On Wed, Feb 24, 2021 at 04:50:39PM -0700, Yu Zhao wrote:
> On Wed, Feb 24, 2021 at 10:48:46PM +0000, Matthew Wilcox wrote:
> > On Wed, Feb 24, 2021 at 03:34:16PM -0700, Yu Zhao wrote:
> > > > If only somebody were working on a patch series to get rid of
> > > > all those calls to compound_head()! Some reviews on
> > > > https://lore.kernel.org/linux-mm/20210128070404.1922318-2-willy@infradead.org/
> > > > would be nice.
> > >
> > > I'm on board with the idea and have done some research in this
> > > direction. We've found that the ideal *anon* page size for Chrome OS
> > > is not 4KB or 2MB, but 32KB. I hope we could leverage the folio to
> > > support flexible anon page size to reduce the number of page faults
> > > (vs 4KB) or internal fragmentation (vs 2MB).
> > >
> > > That being said, it seems to me this is a long term plan and right
> > > now we need something smaller. So if you don't mind, I'll just go
> > > ahead and remove compound_head() from Page{LRU,Active,Unevictable,
> > > SwapBacked} first?
> >
> > It's really not a big change I'm suggesting here. You need
> > https://lore.kernel.org/linux-mm/20210128070404.1922318-2-willy@infradead.org/
> > https://lore.kernel.org/linux-mm/20210128070404.1922318-5-willy@infradead.org/
> > https://lore.kernel.org/linux-mm/20210128070404.1922318-8-willy@infradead.org/
> > and then the patch I sent above to create folio_lru().
> >
> > Then any changes you want to make to use folios more broadly will
> > incrementally move us towards your goal of 32kB anon pages.
>
> Well, these patches introduce a new concept which I'm on board with.
It's not really a new concept ... it's a new type for an existing concept
(a head page).
> Assume everybody else is too, it still seems to me it's an overkill
> to employee folio to just get rid of unnecessary compound_head()
> in page_lru() -- this is not a criticism but a compliment.
It's not overkill, that really is the point of a folio! If you
think about it, only head pages can be on the LRU list (because the
compound_head is in the union with the lru list_head). So it
always makes sense to talk about folios on the LRU list.
> Let me work out something *conceptually* smaller first, and if you
> think folio is absolutely more suitable even for this specific issue,
> I'll go review and test the four patches you listed. Sounds good?
Umm. It seems to me that no matter what you do, it'll be equivalent to
this, only without the type-safety?
next prev parent reply other threads:[~2021-02-25 3:57 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-22 22:05 [PATCH v2 00/10] mm: lru related cleanups Yu Zhao
2021-01-22 22:05 ` [PATCH v2 01/10] mm: use add_page_to_lru_list() Yu Zhao
2021-01-26 18:57 ` Vlastimil Babka
2021-01-27 2:12 ` Miaohe Lin
2021-01-22 22:05 ` [PATCH v2 02/10] mm: shuffle lru list addition and deletion functions Yu Zhao
2021-01-26 18:58 ` Vlastimil Babka
2021-01-27 2:14 ` Miaohe Lin
2021-01-22 22:05 ` [PATCH v2 03/10] mm: don't pass "enum lru_list" to lru list addition functions Yu Zhao
2021-01-26 19:13 ` Vlastimil Babka
2021-01-26 21:34 ` Yu Zhao
2021-01-27 10:51 ` Vlastimil Babka
2021-01-26 22:01 ` Matthew Wilcox
2021-01-26 22:14 ` Yu Zhao
2021-02-23 22:50 ` Andrew Morton
2021-02-24 5:29 ` Yu Zhao
2021-02-24 8:06 ` Alex Shi
2021-02-24 8:37 ` Yu Zhao
2021-02-24 9:01 ` Alex Shi
2021-01-22 22:05 ` [PATCH v2 04/10] mm: don't pass "enum lru_list" to trace_mm_lru_insertion() Yu Zhao
2021-01-22 22:05 ` [PATCH v2 05/10] mm: don't pass "enum lru_list" to del_page_from_lru_list() Yu Zhao
2021-01-22 22:05 ` [PATCH v2 06/10] mm: add __clear_page_lru_flags() to replace page_off_lru() Yu Zhao
2021-01-22 22:05 ` [PATCH v2 07/10] mm: VM_BUG_ON lru page flags Yu Zhao
2021-01-22 22:05 ` [PATCH v2 08/10] mm: fold page_lru_base_type() into its sole caller Yu Zhao
2021-01-22 22:05 ` [PATCH v2 09/10] mm: fold __update_lru_size() " Yu Zhao
2021-01-22 22:06 ` [PATCH v2 10/10] mm: make lruvec_lru_size() static Yu Zhao
2021-02-24 8:48 ` [PATCH] mm: test page->flags directly in page_lru() Yu Zhao
2021-02-24 13:15 ` Andrew Morton
2021-02-24 19:57 ` Yu Zhao
2021-02-24 21:56 ` Matthew Wilcox
2021-02-24 22:34 ` Yu Zhao
2021-02-24 22:48 ` Matthew Wilcox
2021-02-24 23:50 ` Yu Zhao
2021-02-25 3:55 ` Matthew Wilcox [this message]
2021-02-25 5:22 ` Yu Zhao
2021-02-25 12:12 ` Matthew Wilcox
2021-02-26 9:17 ` [PATCH v2 0/3] trim the uses of compound_head() Yu Zhao
2021-02-26 9:17 ` [PATCH v2 1/3] mm: bypass compound_head() for PF_NO_TAIL when enforce=1 Yu Zhao
2021-02-26 9:17 ` [PATCH v2 2/3] mm: use PF_NO_TAIL for PG_lru Yu Zhao
2021-02-26 20:22 ` Yu Zhao
2021-02-26 9:17 ` [PATCH v2 3/3] mm: use PF_ONLY_HEAD for PG_active and PG_unevictable Yu Zhao
2021-02-26 12:13 ` Matthew Wilcox
2021-02-26 19:49 ` Yu Zhao
2021-02-26 20:27 ` Matthew Wilcox
2021-03-01 11:50 ` Kirill A. Shutemov
2021-03-01 19:58 ` Yu Zhao
2021-03-01 20:16 ` Hugh Dickins
2021-03-01 20:26 ` Matthew Wilcox
2021-02-26 10:52 ` [PATCH v2 0/3] trim the uses of compound_head() Vlastimil Babka
2021-02-26 19:04 ` Yu Zhao
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