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b=cvOmlvkR9omRAL+z5koDiA3lYIQCIzzOy/epDpUKdm+tiQ1JCLW5RIMUy/ckma01o p6Bz7FcGd+1Nr8WqCJx/ppZgVN8SXBJ9HwdcqEyJaZhDLhxw6vT6iag8ESefjwzbLD 0biPP5VDtEdR70LAIPqOH/mJtFsZzszR0Uaa6eRJidBl6hjzAoWhLgp8Uz9j5gwE52 YReQahWGnm6P5od6pbkSxEDPenbZX4pLb4Ebmq9/OX+kmlDDMq1DuEMOmnGBGvMZf+ pf9RVOM+GzlLeE3kljkvuwdHyrZaEEZtxThTibHUXNp50tgycfTK0YoffR+PaBhpWo QgjTO6359DUfw== Date: Fri, 24 May 2024 11:52:21 +0300 From: Mike Rapoport To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , "Matthew Wilcox (Oracle)" , Minchan Kim , Sergey Senozhatsky , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH RFC 3/6] mm/zsmalloc: use a proper page type Message-ID: References: <20240522210341.1030552-1-david@redhat.com> <20240522210341.1030552-4-david@redhat.com> <2563ea6b-7c65-46a0-adf3-552f2e863c94@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2563ea6b-7c65-46a0-adf3-552f2e863c94@redhat.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 4B1E110000B X-Stat-Signature: phfu7n5zrzpuy5p5bfr9e43wjx87sjzx X-HE-Tag: 1716540856-70907 X-HE-Meta: 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 K8WG8Dxt xe5qeh55FzvYLEjyfhUaEmavVCsMH6NQYAMKSVCuukCnute44Vg1Vqx1cPOBMPwfUzUc0BYHfLwy10OQ+P5rYicTwns5qsMe7SenAFpvHRgV3IMC56mVZa3VR6c5sHPR2VG3JfklRK4hDk/VWX9+hiymTHrDg3sT9QH8pzcetij7fm9pGnXUIsRVx87LgUT4s6FhFIyL/Bjw+8B3j7MICVlMQADgTepst8zB1P+j1h8uv8ZSYW18LjJXJ+9GpO/dMEgalKRGGP9hEEIpdigTcX5s/FjMpDsALPGNCd5yhDzufUvFHH2T/NFs1lKL+fYuxd42XgUTUAIdrCel6MTPUy8YWwjqNhxKnK/2VPp/yI8zMBQU= 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: List-Subscribe: List-Unsubscribe: On Thu, May 23, 2024 at 04:55:44PM +0200, David Hildenbrand wrote: > On 22.05.24 23:03, David Hildenbrand wrote: > > Let's clean it up: use a proper page type and store our data (offset > > into a page) in the lower 16 bit as documented. > > > > We'll have to restrict ourselves to <= 64KB base page size (so the offset > > fits into 16 bit), which sounds reasonable. Unfortunately, we don't have > > any space to store it elsewhere for now. > > > > Based on this, we should do a proper "struct zsdesc" conversion, as > > proposed in [1]. > > > > This removes the last _mapcount/page_type offender. > > > > [1] https://lore.kernel.org/all/20231130101242.2590384-1-42.hyeyoo@gmail.com/ > > > > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> > > Signed-off-by: David Hildenbrand > > --- > > include/linux/page-flags.h | 3 +++ > > mm/Kconfig | 1 + > > mm/zsmalloc.c | 23 +++++++++++++++++++---- > > 3 files changed, 23 insertions(+), 4 deletions(-) > > > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > > index ed9ac4b5233d..ccaf16656de9 100644 > > --- a/include/linux/page-flags.h > > +++ b/include/linux/page-flags.h > > @@ -959,6 +959,7 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) > > #define PG_guard 0x00080000 > > #define PG_hugetlb 0x00100800 > > #define PG_slab 0x00200000 > > +#define PG_zsmalloc 0x00400000 > > #define PageType(page, flag) \ > > ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) > > @@ -1073,6 +1074,8 @@ FOLIO_TYPE_OPS(hugetlb, hugetlb) > > FOLIO_TEST_FLAG_FALSE(hugetlb) > > #endif > > +PAGE_TYPE_OPS(Zsmalloc, zsmalloc, zsmalloc) > > + > > /** > > * PageHuge - Determine if the page belongs to hugetlbfs > > * @page: The page to test. > > diff --git a/mm/Kconfig b/mm/Kconfig > > index b4cb45255a54..0371d79b1b75 100644 > > --- a/mm/Kconfig > > +++ b/mm/Kconfig > > @@ -190,6 +190,7 @@ config ZSMALLOC > > tristate > > prompt "N:1 compression allocator (zsmalloc)" if ZSWAP > > depends on MMU > > + depends on PAGE_SIZE_LESS_THAN_256KB # we want <= 64KB > > help > > zsmalloc is a slab-based memory allocator designed to store > > pages of various compression levels efficiently. It achieves > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > > index b42d3545ca85..6f0032e06242 100644 > > --- a/mm/zsmalloc.c > > +++ b/mm/zsmalloc.c > > @@ -20,7 +20,8 @@ > > * page->index: links together all component pages of a zspage > > * For the huge page, this is always 0, so we use this field > > * to store handle. > > - * page->page_type: first object offset in a subpage of zspage > > + * page->page_type: PG_zsmalloc, lower 16 bit locate the first object > > + * offset in a subpage of a zspage > > * > > * Usage of struct page flags: > > * PG_private: identifies the first component page > > @@ -450,14 +451,22 @@ static inline struct page *get_first_page(struct zspage *zspage) > > return first_page; > > } > > +static inline void reset_first_obj_offset(struct page *page) > > +{ > > + page->page_type |= 0xffff; > > +} > > + > > static inline unsigned int get_first_obj_offset(struct page *page) > > { > > - return page->page_type; > > + return page->page_type & 0xffff; > > } > > static inline void set_first_obj_offset(struct page *page, unsigned int offset) > > { > > - page->page_type = offset; > > + BUILD_BUG_ON(PAGE_SIZE & ~0xffff); > > Buildbot is correctly complaining with PAGE_SIZE=64KiB. > > We must check BUILD_BUG_ON((PAGE_SIZE -1) & ~0xffff); Won't BUILD_BUG_ON(PAGE_SIZE > SZ_64K) be clearer? > -- > Cheers, > > David / dhildenb > > -- Sincerely yours, Mike.