| Message ID | 20201103152237.9853-3-vbabka@suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | cleanup page poisoning | expand |
On 03.11.20 16:22, 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. > > The function kernel_poison_pages() is also called unconditionally and does > the static key check inside. Remove it from there and put it to callers. Also > split it to two functions kernel_poison_pages() and kernel_unpoison_pages() > instead of the confusing bool parameter. > > 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_and_hardening() to enable a single static key instead of > having two static branches in page_poisoning_enabled_static(). [...] > + * 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)); As already mentioned IIRC: return static_branch_unlikely(&_page_poisoning_enabled); > +} > #else > static inline bool page_poisoning_enabled(void) { return false; } > -static inline void kernel_poison_pages(struct page *page, int numpages, > - int enable) { } > +static inline bool page_poisoning_enabled_static(void) { return false; } > +static inline void kernel_poison_pages(struct page *page, int numpages) { } > +static inline void kernel_unpoison_pages(struct page *page, int numpages) { } > #endif > > DECLARE_STATIC_KEY_FALSE(init_on_alloc); > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 44d596c9c764..fd7f9345adc0 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -775,6 +775,17 @@ void init_mem_debugging_and_hardening(void) > static_branch_enable(&init_on_free); > } > > +#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())) > + static_branch_enable(&_page_poisoning_enabled); > +#endif > + > #ifdef CONFIG_DEBUG_PAGEALLOC > if (!debug_pagealloc_enabled()) > return; > @@ -1260,7 +1271,8 @@ static __always_inline bool free_pages_prepare(struct page *page, > if (want_init_on_free()) > kernel_init_free_pages(page, 1 << order); > > - kernel_poison_pages(page, 1 << order, 0); > + if (page_poisoning_enabled_static()) > + kernel_poison_pages(page, 1 << order); This would look much better by having kernel_poison_pages() simply be implemented in a header, where the static check is performed. Take a look at how it's handled in mm/shuffle.h
On 11/11/20 4:38 PM, David Hildenbrand wrote: > On 03.11.20 16:22, 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. >> >> The function kernel_poison_pages() is also called unconditionally and does >> the static key check inside. Remove it from there and put it to callers. Also >> split it to two functions kernel_poison_pages() and kernel_unpoison_pages() >> instead of the confusing bool parameter. >> >> 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_and_hardening() to enable a single static key instead of >> having two static branches in page_poisoning_enabled_static(). > > [...] > >> + * 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)); > > As already mentioned IIRC: Yes, it was, and I thought I fixed it. Guess not. > return static_branch_unlikely(&_page_poisoning_enabled); > >> +} >> @@ -1260,7 +1271,8 @@ static __always_inline bool free_pages_prepare(struct page *page, >> if (want_init_on_free()) >> kernel_init_free_pages(page, 1 << order); >> >> - kernel_poison_pages(page, 1 << order, 0); >> + if (page_poisoning_enabled_static()) >> + kernel_poison_pages(page, 1 << order); > > This would look much better by having kernel_poison_pages() simply be > implemented in a header, where the static check is performed. > > Take a look at how it's handled in mm/shuffle.h Ok. Fixup below. ----8<---- From 7ce26ba61296f583f0f9089e7887f07424f25d2c Mon Sep 17 00:00:00 2001 From: Vlastimil Babka <vbabka@suse.cz> Date: Thu, 12 Nov 2020 15:20:58 +0100 Subject: [PATCH] mm, page_poison: use static key more efficiently-fix Non-functional cleanups, per David Hildenbrand. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> --- include/linux/mm.h | 16 +++++++++++++--- mm/page_alloc.c | 7 +++---- mm/page_poison.c | 4 ++-- 3 files changed, 18 insertions(+), 9 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 4d6dd9f44571..861b9392b5dc 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2867,8 +2867,8 @@ extern int apply_to_existing_page_range(struct mm_struct *mm, extern void init_mem_debugging_and_hardening(void); #ifdef CONFIG_PAGE_POISONING -extern void kernel_poison_pages(struct page *page, int numpages); -extern void kernel_unpoison_pages(struct page *page, int numpages); +extern void __kernel_poison_pages(struct page *page, int numpages); +extern void __kernel_unpoison_pages(struct page *page, int numpages); extern bool _page_poisoning_enabled_early; DECLARE_STATIC_KEY_FALSE(_page_poisoning_enabled); static inline bool page_poisoning_enabled(void) @@ -2881,7 +2881,17 @@ static inline bool page_poisoning_enabled(void) */ static inline bool page_poisoning_enabled_static(void) { - return (static_branch_unlikely(&_page_poisoning_enabled)); + return static_branch_unlikely(&_page_poisoning_enabled); +} +static inline void kernel_poison_pages(struct page *page, int numpages) +{ + if (page_poisoning_enabled_static()) + __kernel_poison_pages(page, numpages); +} +static inline void kernel_unpoison_pages(struct page *page, int numpages) +{ + if (page_poisoning_enabled_static()) + __kernel_unpoison_pages(page, numpages); } #else static inline bool page_poisoning_enabled(void) { return false; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index fd7f9345adc0..1388b5939551 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1271,8 +1271,8 @@ static __always_inline bool free_pages_prepare(struct page *page, if (want_init_on_free()) kernel_init_free_pages(page, 1 << order); - if (page_poisoning_enabled_static()) - kernel_poison_pages(page, 1 << order); + kernel_poison_pages(page, 1 << order); + /* * arch_free_page() can make the page's contents inaccessible. s390 * does this. So nothing which can access the page's contents should @@ -2281,8 +2281,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order, if (debug_pagealloc_enabled_static()) kernel_map_pages(page, 1 << order, 1); kasan_alloc_pages(page, order); - if (page_poisoning_enabled_static()) - kernel_unpoison_pages(page, 1 << order); + kernel_unpoison_pages(page, 1 << order); set_page_owner(page, order, gfp_flags); } diff --git a/mm/page_poison.c b/mm/page_poison.c index dd7aeada036f..4d75fc9ccc7a 100644 --- a/mm/page_poison.c +++ b/mm/page_poison.c @@ -30,7 +30,7 @@ static void poison_page(struct page *page) kunmap_atomic(addr); } -void kernel_poison_pages(struct page *page, int n) +void __kernel_poison_pages(struct page *page, int n) { int i; @@ -89,7 +89,7 @@ static void unpoison_page(struct page *page) kunmap_atomic(addr); } -void kernel_unpoison_pages(struct page *page, int n) +void __kernel_unpoison_pages(struct page *page, int n) { int i;
On 12.11.20 15:37, Vlastimil Babka wrote: > On 11/11/20 4:38 PM, David Hildenbrand wrote: >> On 03.11.20 16:22, 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. >>> >>> The function kernel_poison_pages() is also called unconditionally and does >>> the static key check inside. Remove it from there and put it to callers. Also >>> split it to two functions kernel_poison_pages() and kernel_unpoison_pages() >>> instead of the confusing bool parameter. >>> >>> 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_and_hardening() to enable a single static key instead of >>> having two static branches in page_poisoning_enabled_static(). >> >> [...] >> >>> + * 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)); >> >> As already mentioned IIRC: > > Yes, it was, and I thought I fixed it. Guess not. > >> return static_branch_unlikely(&_page_poisoning_enabled); >> >>> +} > >>> @@ -1260,7 +1271,8 @@ static __always_inline bool free_pages_prepare(struct page *page, >>> if (want_init_on_free()) >>> kernel_init_free_pages(page, 1 << order); >>> >>> - kernel_poison_pages(page, 1 << order, 0); >>> + if (page_poisoning_enabled_static()) >>> + kernel_poison_pages(page, 1 << order); >> >> This would look much better by having kernel_poison_pages() simply be >> implemented in a header, where the static check is performed. >> >> Take a look at how it's handled in mm/shuffle.h > > Ok. Fixup below. > > ----8<---- > > From 7ce26ba61296f583f0f9089e7887f07424f25d2c Mon Sep 17 00:00:00 2001 > From: Vlastimil Babka <vbabka@suse.cz> > Date: Thu, 12 Nov 2020 15:20:58 +0100 > Subject: [PATCH] mm, page_poison: use static key more efficiently-fix > > Non-functional cleanups, per David Hildenbrand. > > Signed-off-by: Vlastimil Babka <vbabka@suse.cz> > --- > include/linux/mm.h | 16 +++++++++++++--- > mm/page_alloc.c | 7 +++---- > mm/page_poison.c | 4 ++-- > 3 files changed, 18 insertions(+), 9 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 4d6dd9f44571..861b9392b5dc 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2867,8 +2867,8 @@ extern int apply_to_existing_page_range(struct mm_struct *mm, > > extern void init_mem_debugging_and_hardening(void); > #ifdef CONFIG_PAGE_POISONING > -extern void kernel_poison_pages(struct page *page, int numpages); > -extern void kernel_unpoison_pages(struct page *page, int numpages); > +extern void __kernel_poison_pages(struct page *page, int numpages); > +extern void __kernel_unpoison_pages(struct page *page, int numpages); > extern bool _page_poisoning_enabled_early; > DECLARE_STATIC_KEY_FALSE(_page_poisoning_enabled); > static inline bool page_poisoning_enabled(void) > @@ -2881,7 +2881,17 @@ static inline bool page_poisoning_enabled(void) > */ > static inline bool page_poisoning_enabled_static(void) > { > - return (static_branch_unlikely(&_page_poisoning_enabled)); > + return static_branch_unlikely(&_page_poisoning_enabled); > +} > +static inline void kernel_poison_pages(struct page *page, int numpages) > +{ > + if (page_poisoning_enabled_static()) > + __kernel_poison_pages(page, numpages); > +} > +static inline void kernel_unpoison_pages(struct page *page, int numpages) > +{ > + if (page_poisoning_enabled_static()) > + __kernel_unpoison_pages(page, numpages); > } > #else > static inline bool page_poisoning_enabled(void) { return false; } > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index fd7f9345adc0..1388b5939551 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1271,8 +1271,8 @@ static __always_inline bool free_pages_prepare(struct page *page, > if (want_init_on_free()) > kernel_init_free_pages(page, 1 << order); > > - if (page_poisoning_enabled_static()) > - kernel_poison_pages(page, 1 << order); > + kernel_poison_pages(page, 1 << order); > + > /* > * arch_free_page() can make the page's contents inaccessible. s390 > * does this. So nothing which can access the page's contents should > @@ -2281,8 +2281,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order, > if (debug_pagealloc_enabled_static()) > kernel_map_pages(page, 1 << order, 1); > kasan_alloc_pages(page, order); > - if (page_poisoning_enabled_static()) > - kernel_unpoison_pages(page, 1 << order); > + kernel_unpoison_pages(page, 1 << order); > set_page_owner(page, order, gfp_flags); > } > > diff --git a/mm/page_poison.c b/mm/page_poison.c > index dd7aeada036f..4d75fc9ccc7a 100644 > --- a/mm/page_poison.c > +++ b/mm/page_poison.c > @@ -30,7 +30,7 @@ static void poison_page(struct page *page) > kunmap_atomic(addr); > } > > -void kernel_poison_pages(struct page *page, int n) > +void __kernel_poison_pages(struct page *page, int n) > { > int i; > > @@ -89,7 +89,7 @@ static void unpoison_page(struct page *page) > kunmap_atomic(addr); > } > > -void kernel_unpoison_pages(struct page *page, int n) > +void __kernel_unpoison_pages(struct page *page, int n) > { > int i; > > LGTM.
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 481611c09dae..e53faed6ba93 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -1116,7 +1116,7 @@ static int virtballoon_validate(struct virtio_device *vdev) */ if (!want_init_on_free() && (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) || - !page_poisoning_enabled())) + !page_poisoning_enabled_static())) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING); diff --git a/include/linux/mm.h b/include/linux/mm.h index e0bc1c8aa2a6..4d6dd9f44571 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2867,12 +2867,27 @@ extern int apply_to_existing_page_range(struct mm_struct *mm, extern void init_mem_debugging_and_hardening(void); #ifdef CONFIG_PAGE_POISONING -extern bool page_poisoning_enabled(void); -extern void kernel_poison_pages(struct page *page, int numpages, int enable); +extern void kernel_poison_pages(struct page *page, int numpages); +extern void kernel_unpoison_pages(struct page *page, int numpages); +extern bool _page_poisoning_enabled_early; +DECLARE_STATIC_KEY_FALSE(_page_poisoning_enabled); +static inline bool page_poisoning_enabled(void) +{ + return _page_poisoning_enabled_early; +} +/* + * 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)); +} #else static inline bool page_poisoning_enabled(void) { return false; } -static inline void kernel_poison_pages(struct page *page, int numpages, - int enable) { } +static inline bool page_poisoning_enabled_static(void) { return false; } +static inline void kernel_poison_pages(struct page *page, int numpages) { } +static inline void kernel_unpoison_pages(struct page *page, int numpages) { } #endif DECLARE_STATIC_KEY_FALSE(init_on_alloc); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 44d596c9c764..fd7f9345adc0 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -775,6 +775,17 @@ void init_mem_debugging_and_hardening(void) static_branch_enable(&init_on_free); } +#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())) + static_branch_enable(&_page_poisoning_enabled); +#endif + #ifdef CONFIG_DEBUG_PAGEALLOC if (!debug_pagealloc_enabled()) return; @@ -1260,7 +1271,8 @@ static __always_inline bool free_pages_prepare(struct page *page, if (want_init_on_free()) kernel_init_free_pages(page, 1 << order); - kernel_poison_pages(page, 1 << order, 0); + if (page_poisoning_enabled_static()) + kernel_poison_pages(page, 1 << order); /* * arch_free_page() can make the page's contents inaccessible. s390 * does this. So nothing which can access the page's contents should @@ -2206,7 +2218,7 @@ 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(); } #ifdef CONFIG_DEBUG_VM @@ -2269,7 +2281,8 @@ inline void post_alloc_hook(struct page *page, unsigned int order, if (debug_pagealloc_enabled_static()) kernel_map_pages(page, 1 << order, 1); kasan_alloc_pages(page, order); - kernel_poison_pages(page, 1 << order, 1); + if (page_poisoning_enabled_static()) + kernel_unpoison_pages(page, 1 << order); set_page_owner(page, order, gfp_flags); } diff --git a/mm/page_poison.c b/mm/page_poison.c index ae0482cded87..dd7aeada036f 100644 --- a/mm/page_poison.c +++ b/mm/page_poison.c @@ -8,45 +8,17 @@ #include <linux/ratelimit.h> #include <linux/kasan.h> -static DEFINE_STATIC_KEY_FALSE_RO(want_page_poisoning); +bool _page_poisoning_enabled_early; +EXPORT_SYMBOL(_page_poisoning_enabled_early); +DEFINE_STATIC_KEY_FALSE(_page_poisoning_enabled); +EXPORT_SYMBOL(_page_poisoning_enabled); static int __init early_page_poison_param(char *buf) { - int ret; - bool tmp; - - ret = strtobool(buf, &tmp); - if (ret) - return ret; - - if (tmp) - static_branch_enable(&want_page_poisoning); - else - static_branch_disable(&want_page_poisoning); - - return 0; + return kstrtobool(buf, &_page_poisoning_enabled_early); } early_param("page_poison", early_page_poison_param); -/** - * page_poisoning_enabled - check if page poisoning is enabled - * - * Return true if page poisoning is enabled, or false if not. - */ -bool page_poisoning_enabled(void) -{ - /* - * Assumes that debug_pagealloc_enabled is set before - * memblock_free_all. - * Page poisoning is debug page alloc for some arches. If - * either of those options are enabled, enable poisoning. - */ - return (static_branch_unlikely(&want_page_poisoning) || - (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) && - debug_pagealloc_enabled())); -} -EXPORT_SYMBOL_GPL(page_poisoning_enabled); - static void poison_page(struct page *page) { void *addr = kmap_atomic(page); @@ -58,7 +30,7 @@ static void poison_page(struct page *page) kunmap_atomic(addr); } -static void poison_pages(struct page *page, int n) +void kernel_poison_pages(struct page *page, int n) { int i; @@ -117,7 +89,7 @@ static void unpoison_page(struct page *page) kunmap_atomic(addr); } -static void unpoison_pages(struct page *page, int n) +void kernel_unpoison_pages(struct page *page, int n) { int i; @@ -125,17 +97,6 @@ static void unpoison_pages(struct page *page, int n) unpoison_page(page + i); } -void kernel_poison_pages(struct page *page, int numpages, int enable) -{ - if (!page_poisoning_enabled()) - return; - - if (enable) - unpoison_pages(page, numpages); - else - poison_pages(page, numpages); -} - #ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC void __kernel_map_pages(struct page *page, int numpages, int enable) {
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. The function kernel_poison_pages() is also called unconditionally and does the static key check inside. Remove it from there and put it to callers. Also split it to two functions kernel_poison_pages() and kernel_unpoison_pages() instead of the confusing bool parameter. 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_and_hardening() 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> --- drivers/virtio/virtio_balloon.c | 2 +- include/linux/mm.h | 23 +++++++++++--- mm/page_alloc.c | 19 ++++++++++-- mm/page_poison.c | 53 +++++---------------------------- 4 files changed, 43 insertions(+), 54 deletions(-)