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[195.135.220.15]) by mx.google.com with ESMTPS id 80si2289141pfz.11.2019.01.30.11.11.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 30 Jan 2019 11:11:25 -0800 (PST) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 6E8A5AD7A; Wed, 30 Jan 2019 19:11:23 +0000 (UTC) Date: Wed, 30 Jan 2019 20:11:17 +0100 From: Michal Hocko To: Dan Williams Cc: akpm@linux-foundation.org, Dave Hansen , Kees Cook , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v9 3/3] mm: Maintain randomization of page free lists Message-ID: <20190130191117.GH18811@dhcp22.suse.cz> References: <154882453052.1338686.16411162273671426494.stgit@dwillia2-desk3.amr.corp.intel.com> <154882454628.1338686.46582179767934746.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <154882454628.1338686.46582179767934746.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 29-01-19 21:02:26, Dan Williams wrote: > When freeing a page with an order >= shuffle_page_order randomly select > the front or back of the list for insertion. > > While the mm tries to defragment physical pages into huge pages this can > tend to make the page allocator more predictable over time. Inject the > front-back randomness to preserve the initial randomness established by > shuffle_free_memory() when the kernel was booted. > > The overhead of this manipulation is constrained by only being applied > for MAX_ORDER sized pages by default. I have asked in v7 but didn't get any response. Do we really ned per free_area random pool? Why a global one is not sufficient? > Cc: Michal Hocko > Cc: Dave Hansen > Reviewed-by: Kees Cook > Signed-off-by: Dan Williams > --- > include/linux/mmzone.h | 12 ++++++++++++ > include/linux/shuffle.h | 12 ++++++++++++ > mm/page_alloc.c | 11 +++++++++-- > mm/shuffle.c | 16 ++++++++++++++++ > 4 files changed, 49 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 6ab8b58c6481..d42aafe23045 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -98,6 +98,10 @@ extern int page_group_by_mobility_disabled; > struct free_area { > struct list_head free_list[MIGRATE_TYPES]; > unsigned long nr_free; > +#ifdef CONFIG_SHUFFLE_PAGE_ALLOCATOR > + u64 rand; > + u8 rand_bits; > +#endif > }; > > /* Used for pages not on another list */ > @@ -116,6 +120,14 @@ static inline void add_to_free_area_tail(struct page *page, struct free_area *ar > area->nr_free++; > } > > +#ifdef CONFIG_SHUFFLE_PAGE_ALLOCATOR > +/* Used to preserve page allocation order entropy */ > +void add_to_free_area_random(struct page *page, struct free_area *area, > + int migratetype); > +#else > +#define add_to_free_area_random add_to_free_area > +#endif > + > /* Used for pages which are on another list */ > static inline void move_to_free_area(struct page *page, struct free_area *area, > int migratetype) > diff --git a/include/linux/shuffle.h b/include/linux/shuffle.h > index bed2d2901d13..649498442aa0 100644 > --- a/include/linux/shuffle.h > +++ b/include/linux/shuffle.h > @@ -29,6 +29,13 @@ static inline void shuffle_zone(struct zone *z) > return; > __shuffle_zone(z); > } > + > +static inline bool is_shuffle_order(int order) > +{ > + if (!static_branch_unlikely(&page_alloc_shuffle_key)) > + return false; > + return order >= SHUFFLE_ORDER; > +} > #else > static inline void shuffle_free_memory(pg_data_t *pgdat) > { > @@ -41,5 +48,10 @@ static inline void shuffle_zone(struct zone *z) > static inline void page_alloc_shuffle(enum mm_shuffle_ctl ctl) > { > } > + > +static inline bool is_shuffle_order(int order) > +{ > + return false; > +} > #endif > #endif /* _MM_SHUFFLE_H */ > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 1cb9a467e451..7895f8bd1a32 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -43,6 +43,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -889,7 +890,8 @@ static inline void __free_one_page(struct page *page, > * so it's less likely to be used soon and more likely to be merged > * as a higher order page > */ > - if ((order < MAX_ORDER-2) && pfn_valid_within(buddy_pfn)) { > + if ((order < MAX_ORDER-2) && pfn_valid_within(buddy_pfn) > + && !is_shuffle_order(order)) { > struct page *higher_page, *higher_buddy; > combined_pfn = buddy_pfn & pfn; > higher_page = page + (combined_pfn - pfn); > @@ -903,7 +905,12 @@ static inline void __free_one_page(struct page *page, > } > } > > - add_to_free_area(page, &zone->free_area[order], migratetype); > + if (is_shuffle_order(order)) > + add_to_free_area_random(page, &zone->free_area[order], > + migratetype); > + else > + add_to_free_area(page, &zone->free_area[order], migratetype); > + > } > > /* > diff --git a/mm/shuffle.c b/mm/shuffle.c > index db517cdbaebe..0da7d1826c6a 100644 > --- a/mm/shuffle.c > +++ b/mm/shuffle.c > @@ -186,3 +186,19 @@ void __meminit __shuffle_free_memory(pg_data_t *pgdat) > for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++) > shuffle_zone(z); > } > + > +void add_to_free_area_random(struct page *page, struct free_area *area, > + int migratetype) > +{ > + if (area->rand_bits == 0) { > + area->rand_bits = 64; > + area->rand = get_random_u64(); > + } > + > + if (area->rand & 1) > + add_to_free_area(page, area, migratetype); > + else > + add_to_free_area_tail(page, area, migratetype); > + area->rand_bits--; > + area->rand >>= 1; > +} > -- Michal Hocko SUSE Labs