From: David Hildenbrand <david@redhat.com>
To: Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Alexander Potapenko <glider@google.com>,
Kees Cook <keescook@chromium.org>,
Michal Hocko <mhocko@kernel.org>,
Mateusz Nosek <mateusznosek0@gmail.com>
Subject: Re: [PATCH 2/3] mm, page_poison: use static key more efficiently
Date: Tue, 27 Oct 2020 10:07:28 +0100 [thread overview]
Message-ID: <4e35c52a-800a-4a60-2ef5-dd70a4f774c6@redhat.com> (raw)
In-Reply-To: <20201026173358.14704-3-vbabka@suse.cz>
On 26.10.20 18:33, Vlastimil Babka wrote:
> Commit 11c9c7edae06 ("mm/page_poison.c: replace bool variable with static key")
> changed page_poisoning_enabled() to a static key check. However, the function
> is not inlined, so each check still involves a function call with overhead not
> eliminated when page poisoning is disabled.
>
> Analogically to how debug_pagealloc is handled, this patch converts
> page_poisoning_enabled() back to boolean check, and introduces
> page_poisoning_enabled_static() for fast paths. Both functions are inlined.
>
> Also optimize the check that enables page poisoning instead of debug_pagealloc
> for architectures without proper debug_pagealloc support. Move the check to
> init_mem_debugging() to enable a single static key instead of having two
> static branches in page_poisoning_enabled_static().
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
[...]
> +/*
> + * For use in fast paths after init_mem_debugging() has run, or when a
> + * false negative result is not harmful when called too early.
> + */
> +static inline bool page_poisoning_enabled_static(void)
> +{
> + return (static_branch_unlikely(&_page_poisoning_enabled));
return static_branch_unlikely(&_page_poisoning_enabled);
> +}
> #else
> static inline bool page_poisoning_enabled(void) { return false; }
> +static inline bool page_poisoning_enabled_static(void) { return false; }
> static inline void kernel_poison_pages(struct page *page, int numpages,
> int enable) { }
> #endif
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index b168c58ef337..2a1be197649d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -777,6 +777,17 @@ void init_mem_debugging()
> }
> }
>
> +#ifdef CONFIG_PAGE_POISONING
> + /*
> + * Page poisoning is debug page alloc for some arches. If
> + * either of those options are enabled, enable poisoning.
> + */
> + if (page_poisoning_enabled() ||
> + (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
> + debug_pagealloc_enabled()))
Weird indentation
if (page_poisoning_enabled() ||
(!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
debug_pagealloc_enabled()))
> + static_branch_enable(&_page_poisoning_enabled);
> +#endif
> +
> #ifdef CONFIG_DEBUG_PAGEALLOC
> if (!debug_pagealloc_enabled())
> return;
> @@ -2208,7 +2219,7 @@ static inline int check_new_page(struct page *page)
> static inline bool free_pages_prezeroed(void)
> {
> return (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) &&
> - page_poisoning_enabled()) || want_init_on_free();
> + page_poisoning_enabled_static()) || want_init_on_free();
> }
Apart from that LGTM.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-10-27 9:07 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 17:33 [PATCH 0/3] optimize handling of memory debugging parameters Vlastimil Babka
2020-10-26 17:33 ` [PATCH 1/3] mm, page_alloc: do not rely on the order of page_poison and init_on_alloc/free parameters Vlastimil Babka
2020-10-27 9:03 ` David Hildenbrand
2020-10-27 9:58 ` Vlastimil Babka
2020-10-27 9:58 ` David Hildenbrand
2020-10-28 8:31 ` Mike Rapoport
2020-10-26 17:33 ` [PATCH 2/3] mm, page_poison: use static key more efficiently Vlastimil Babka
2020-10-27 9:07 ` David Hildenbrand [this message]
2020-10-30 16:27 ` Luis Chamberlain
2020-10-30 22:56 ` Vlastimil Babka
2020-11-11 13:29 ` Luis Chamberlain
2020-10-26 17:33 ` [PATCH 3/3] mm, page_alloc: reduce static keys in prep_new_page() Vlastimil Babka
2020-10-27 9:10 ` David Hildenbrand
2020-10-27 11:05 ` Vlastimil Babka
2020-10-27 13:32 ` Vlastimil Babka
2020-10-27 17:41 ` Vlastimil Babka
2020-10-28 8:38 ` David Hildenbrand
2020-10-29 17:37 ` Alexander Potapenko
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