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c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1PkJLLTHTHGvD+6CtGT0JeNBynTOmH00lzXh1tBHgdk=; b=QT18mwPpI7Qvg7Rw0SGsnEO2ogjlHMuKGsL7h+KyLjUxXDgNYqOaF3K8ARqNmu8jmK 7y4K5WvNFz5XFb1UCpsJ+gXImPvgQBMyUjspUwd2oY0SELB4fgzLnc0I+RoIPj8HAr8h V62XPHsl77hm99Q4dfsB2eVF5paNJINB1oc55RozY8EZNho25t4XDkp7hDN590WbI2f+ PRAkXRfSasW7ryErv1NVJI0eCQ2nf9D0T2Hd98OpecnFBmO2BGsOojRS2JsAHTAu4OQ+ n2J+d/YnBP21PV1LQXCjmhI8Y5gD0j5DE4KAc8Pe33Egb8F3K7y0SoEwYdcMpjkBD+nd G+ig== X-Gm-Message-State: AOAM533AMTY1CFTta/THRgJkhK5n9u0Sv3sPiNNPcMq6h7igXq7iC236 S4/OZMp708ZfL+RVPLer/PxMpj/vNF6eUXopkwEIqQ== X-Google-Smtp-Source: ABdhPJxKovdhcbkAgrBDEdjMU7ZJHmMEXN8Mq3F1RYkM6JeOu075ftsAAt6nPr79OpJpAUY1RCGxxxOksG4bUMsVeKQ= X-Received: by 2002:a63:594a:: with SMTP id j10mr25427312pgm.341.1606101336098; Sun, 22 Nov 2020 19:15:36 -0800 (PST) MIME-Version: 1.0 References: <20201120064325.34492-1-songmuchun@bytedance.com> <20201120064325.34492-22-songmuchun@bytedance.com> <20201120082552.GI3200@dhcp22.suse.cz> <20201122190002.GH4327@casper.infradead.org> In-Reply-To: <20201122190002.GH4327@casper.infradead.org> From: Muchun Song Date: Mon, 23 Nov 2020 11:14:59 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v5 21/21] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two To: Matthew Wilcox Cc: Michal Hocko , Jonathan Corbet , Mike Kravetz , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Oscar Salvador , "Song Bao Hua (Barry Song)" , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" 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 Mon, Nov 23, 2020 at 3:00 AM Matthew Wilcox wrote: > > On Fri, Nov 20, 2020 at 09:25:52AM +0100, Michal Hocko wrote: > > On Fri 20-11-20 14:43:25, Muchun Song wrote: > > > We only can free the unused vmemmap to the buddy system when the > > > size of struct page is a power of two. > > > > Can we actually have !power_of_2 struct pages? > > Yes. On x86-64, if you don't enable MEMCG, it's 56 bytes. On SPARC64, > if you do enable MEMCG, it's 72 bytes. On 32-bit systems, it's > anything from 32-44 bytes, depending on MEMCG, WANT_PAGE_VIRTUAL and > LAST_CPUPID_NOT_IN_PAGE_FLAGS. > On x86-64, even if you do not enable MEMCG, it's also 64 bytes. Because CONFIG_HAVE_ALIGNED_STRUCT_PAGE is defined if we use SLUB. -- Yours, Muchun