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 12:12:07 +0000 [thread overview]
Message-ID: <20210225121207.GY2858050@casper.infradead.org> (raw)
In-Reply-To: <YDc0Hqk+A4wvN7jg@google.com>
On Wed, Feb 24, 2021 at 10:22:38PM -0700, Yu Zhao wrote:
> On Thu, Feb 25, 2021 at 03:55:53AM +0000, Matthew Wilcox wrote:
> > On Wed, Feb 24, 2021 at 04:50:39PM -0700, Yu Zhao wrote:
> > > 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?
>
> I'm thinking about something trivial but still very effective. So far
> I've only tested it with PG_{active,unevictable}, and I'm already
> seeing a 4KB gain less the 2KB loss from page_lru().
>
> I didn't go with this at the beginning because it's also time-
> consuming. I need to go over every single use of
> PG_{active,unevictable,swapbacked,lru}.
Well, yes. If you went with the folio, it'd also be typesafe.
What you've done here makes it a runtime error, and it's only detected
if you enable CONFIG_DEBUG_VM_PGFLAGS, which people don't do, in general.
> +++ b/fs/proc/task_mmu.c
> @@ -1712,6 +1712,7 @@ static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty,
> unsigned long nr_pages)
> {
> int count = page_mapcount(page);
> + struct page *head = compound_head(page);
>
> md->pages += nr_pages;
> if (pte_dirty || PageDirty(page))
... if you went full-on folio in this function, you could also make this
FolioDirty, saving another call to compound_head.
> @@ -1720,7 +1721,7 @@ static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty,
> if (PageSwapCache(page))
... ditto ...
> md->swapcache += nr_pages;
>
> - if (PageActive(page) || PageUnevictable(page))
> + if (PageActive(head) || PageUnevictable(head))
> md->active += nr_pages;
>
> if (PageWriteback(page))
... ditto...
next prev parent reply other threads:[~2021-02-25 12:12 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
2021-02-25 5:22 ` Yu Zhao
2021-02-25 12:12 ` Matthew Wilcox [this message]
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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