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Mon, 30 Sep 2019 09:19:39 +1000 (AEST) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate16.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Sun, 29 Sep 2019 16:19:42 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Sun, 29 Sep 2019 16:19:35 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Sun, 29 Sep 2019 16:19:35 -0700 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL111.nvidia.com (172.20.187.18) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Sun, 29 Sep 2019 23:19:35 +0000 Received: from [10.2.173.141] (172.20.13.39) by DRHQMAIL107.nvidia.com (10.27.9.16) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Sun, 29 Sep 2019 23:19:34 +0000 Subject: Re: [PATCH v4 01/11] powerpc/mm: Adds counting method to monitor lockless pgtable walks From: John Hubbard To: Leonardo Bras , , , , , References: <20190927234008.11513-1-leonardo@linux.ibm.com> <20190927234008.11513-2-leonardo@linux.ibm.com> <4ff1e8e8-929b-9cfc-9bf8-ee88e34de888@nvidia.com> X-Nvconfidentiality: public Message-ID: Date: Sun, 29 Sep 2019 16:17:20 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <4ff1e8e8-929b-9cfc-9bf8-ee88e34de888@nvidia.com> X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To DRHQMAIL107.nvidia.com (10.27.9.16) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1569799183; bh=cuUpAejunirY1oVB4xqJhAFbQh4uc7B1ykg3wBoKKZs=; h=X-PGP-Universal:Subject:From:To:CC:References:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=YjWTNeT0CKiy9o+jGIp6KtWT7AvUC9MjQefsgmJQTtk7jdKDbA6WjFQ9JoKMOVBVx 6C7SwiTGmjYkn5+tZPcgR0XtRz7TfihkWkQORs+3CDC+f0s8P4fPbHRlQl7oe3HAZW nrxf5kbcgk+ker4DiB23UJ2izp3Os3fz8miMQxXdGrwPK8X5Lt+idjpD6foHYfWZVr w3ztaYXbj0fG9ryOzoGhDspATQNBZuyoeb3i/cvNce3LrgwKUfLxo5qJNZT3gtZsI4 NOz4ZBOs6z/j4VuUFKxFcU1NF9kxF4C22OplZjoArvqsyPljPn2jofEe5dcLYmdJe5 CuLqlhxPTaTCA== X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Keith Busch , Thomas Gleixner , Arnd Bergmann , Greg Kroah-Hartman , YueHaibing , Nicholas Piggin , Mike Rapoport , Mahesh Salgaonkar , Jason Gunthorpe , Paul Mackerras , "Aneesh Kumar K.V" , Ganesh Goudar , Andrew Morton , Ira Weiny , Dan Williams , Allison Randal Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 9/29/19 3:40 PM, John Hubbard wrote: > On 9/27/19 4:39 PM, Leonardo Bras wrote: ... > +config LOCKLESS_PAGE_TABLE_WALK_TRACKING > +=C2=A0=C2=A0=C2=A0 bool "Tracking (and optimization) of lockless page ta= ble walkers" > +=C2=A0=C2=A0=C2=A0 default n > + > +=C2=A0=C2=A0=C2=A0 help > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Maintain a reference count of active lock= less page table > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 walkers. This adds 4 bytes to struct mm s= ize, and two atomic > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 operations to calls such as get_user_page= s_fast(). Some > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 architectures can optimize page table ope= rations if this > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 is enabled. > + > =C2=A0endmenu Actually, the above should be an internal-only config option (PPC arch can auto-select it), so just: +config LOCKLESS_PAGE_TABLE_WALK_TRACKING + bool ...because it's entirely up to other code (as opposed to other people) as to whether this should be selected. I got carried away. :) thanks, --=20 John Hubbard NVIDIA