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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id m6si9472356pll.86.2019.02.11.04.12.11 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 11 Feb 2019 04:12:11 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=knF1plx4; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=BPtXQOxeYch/V0X+MBJp9wTl973Cc6vheZfDDJ3vJ1M=; b=knF1plx4j7WuqTz9tOcA7myib 6p3FyKk+tbMpsSd/mVBx2nyHUziOgR2nxHufUUq8xgF+i23LnegLWIDZBDw1yID6TccRsHBgX098r wpvnaFbVc5Jx54K+xqAypmZG4OhLOuK8oESV01holg8Wu3tNMT9x/bkFZAdkNo9d9rj3TjoYx99ad bdmsboI8goqhAoKeAS4SiMw4oY0phQ/PE0ewAYxD92Jpub+1VDkRidQfYis9w8vdBuaSVSIqez5Iu PjV5o4hOtyDvZ9lFXKTqXdSyc8CDfuqmMc3OuNi0yZYqrwTEOR+TRvedM96Hx+8JavPwlOe10bzwa V9vQRBwBQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gtARU-00075I-CL; Mon, 11 Feb 2019 12:12:08 +0000 Date: Mon, 11 Feb 2019 04:12:08 -0800 From: Matthew Wilcox To: Tariq Toukan Cc: Ilias Apalodimas , David Miller , "brouer@redhat.com" , "toke@redhat.com" , "netdev@vger.kernel.org" , "mgorman@techsingularity.net" , "linux-mm@kvack.org" Subject: Re: [RFC, PATCH] net: page_pool: Don't use page->private to store dma_addr_t Message-ID: <20190211121208.GB12668@bombadil.infradead.org> References: <1549550196-25581-1-git-send-email-ilias.apalodimas@linaro.org> <20190207150745.GW21860@bombadil.infradead.org> <20190207152034.GA3295@apalos> <20190207.132519.1698007650891404763.davem@davemloft.net> <20190207213400.GA21860@bombadil.infradead.org> <20190207214237.GA10676@Iliass-MBP.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) 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, Feb 11, 2019 at 08:53:19AM +0000, Tariq Toukan wrote: > It's great to use the struct page to store its dma mapping, but I am > worried about extensibility. > page_pool is evolving, and it would need several more per-page fields. > One of them would be pageref_bias, a planned optimization to reduce the > number of the costly atomic pageref operations (and replace existing > code in several drivers). There's space for five words (20 or 40 bytes on 32/64 bit).