Messages in this thread Patch in this message | | | Subject | Re: [PATCH 2/3] mm, page_poison: use static key more efficiently | From | David Hildenbrand <> | Date | Tue, 27 Oct 2020 10:07:28 +0100 |
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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
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