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Wed, 25 Nov 2020 05:01:24 -0800 Envelope-to: git@xilinx.com, michal.simek@xilinx.com, stefan.asserhall@xilinx.com, vbabka@suse.cz, rostedt@goodmis.org, shorne@gmail.com, bigeasy@linutronix.de, robin.murphy@arm.com, robh@kernel.org, rdunlap@infradead.org, peterz@infradead.org, penberg@kernel.org, oleg@redhat.com, keescook@chromium.org, joe@perches.com, axboe@kernel.dk, ira.weiny@intel.com, herbert@gondor.apana.org.au, gustavoars@kernel.org, geert@linux-m68k.org, ebiggers@google.com, 0x7f454c46@gmail.com, christian.brauner@ubuntu.com, bhe@redhat.com, nivedita@alum.mit.edu, anshuman.khandual@arm.com, akpm@linux-foundation.org, arnd@arndb.de, monstr@monstr.eu, linux-kernel@vger.kernel.org, rppt@kernel.org, arnd@kernel.org Received: from [172.30.17.109] (port=45816) by smtp.xilinx.com with esmtp (Exim 4.90) (envelope-from ) id 1khuQF-0007Iv-JE; Wed, 25 Nov 2020 05:01:23 -0800 Subject: Re: [PATCH] microblaze: Remove noMMU code To: Arnd Bergmann , Michal Simek CC: Mike Rapoport , "linux-kernel@vger.kernel.org" , Michal Simek , git , Arnd Bergmann , Andrew Morton , Anshuman Khandual , Arvind Sankar , Baoquan He , "Christian Brauner" , Dmitry Safonov <0x7f454c46@gmail.com>, Eric Biggers , "Geert Uytterhoeven" , "Gustavo A. R. Silva" , Herbert Xu , Ira Weiny , Jens Axboe , Joe Perches , Kees Cook , Manish Narani , Oleg Nesterov , Pekka Enberg , "Peter Zijlstra (Intel)" , "Randy Dunlap" , Rob Herring , Robin Murphy , Sebastian Andrzej Siewior , Stafford Horne , Stefan Asserhall , "Steven Rostedt (VMware)" , Vlastimil Babka References: <20201125120739.GO8537@kernel.org> <7217421a-c4de-0bd1-3231-17563e51e3c9@xilinx.com> From: Michal Simek Message-ID: <5947a4da-a08f-049b-9162-628e42980b33@xilinx.com> Date: Wed, 25 Nov 2020 14:01:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-MS-Office365-Filtering-HT: Tenant X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 969e41e9-bfd9-4d15-88b8-08d8914262d4 X-MS-TrafficTypeDiagnostic: SN1PR02MB3855: X-LD-Processed: 657af505-d5df-48d0-8300-c31994686c5c,ExtAddr X-Microsoft-Antispam-PRVS: X-Auto-Response-Suppress: DR, RN, NRN, OOF, AutoReply X-MS-Oob-TLC-OOBClassifiers: OLM:10000; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: dGFyLhCrl3fpigCDKhYGrR3aJQ1ge5k6E4RUIyqe0tBj7799MrFjAi4X7oP1+FPszIDNdzRdWY+8L6tUVuicnR2J8V3f8YKSNkjffSAyvtgUtXemkDGUL7ySqhiBvsD1N+3x7XHuw35ZFwv8C1i96VKwJD3zCHdurJl386sZpCfFutBQwcYpGKYYIOcCx3oAZjo6tj7Ly2U8IRY1cuua6gV4+cfYRWHPSBpty1dMHe9RX/RJ+QktOd+zvyl230xWfcSRcLP26G4Ft7tOnpIvZwEXowE2wMzB1ZeGwKA3v5XXQUyJ/R3N+ex3f2Zwkr9gHDKYZziwX4lUqw/pkYnCZFO/4Q3bdAd4bOAhpvUkZg9a7gK9bzTrmkogZ6JaGzn9iisjgxa6BCn4287BMwc7TqmgLPCCOQ/H4EZT0duvHwxF03ogad2FBfZFlstL9CuHadohv7mvUpw22TvaKcI9qw== X-Forefront-Antispam-Report: CIP:149.199.62.198;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:xsj-pvapexch02.xlnx.xilinx.com;PTR:unknown-62-198.xilinx.com;CAT:NONE;SFS:(4636009)(346002)(396003)(376002)(39860400002)(136003)(46966005)(82310400003)(7416002)(82740400003)(336012)(31696002)(6666004)(4326008)(7636003)(70586007)(70206006)(47076004)(8676002)(186003)(110136005)(53546011)(8936002)(316002)(26005)(54906003)(356005)(36906005)(36756003)(426003)(5660300002)(2616005)(9786002)(31686004)(2906002)(478600001)(44832011)(50156003)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: xilinx.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Nov 2020 13:02:38.3930 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 969e41e9-bfd9-4d15-88b8-08d8914262d4 X-MS-Exchange-CrossTenant-Id: 657af505-d5df-48d0-8300-c31994686c5c X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=657af505-d5df-48d0-8300-c31994686c5c;Ip=[149.199.62.198];Helo=[xsj-pvapexch02.xlnx.xilinx.com] X-MS-Exchange-CrossTenant-AuthSource: CY1NAM02FT051.eop-nam02.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN1PR02MB3855 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25. 11. 20 13:57, Arnd Bergmann wrote: > On Wed, Nov 25, 2020 at 1:14 PM Michal Simek wrote: >> >> And second part. I know I removed that Kconfig macros for it but maybe >> good to talk about what needs to change to support different page size >> for systems with MMU. > > I would recommend just leaving it hardwired to 4K. The benefits of larger > pages are rather questionable, especially on systems without tons of > RAM, and it's an endless source of problems. > > The commit that added the option, ba9c4f88d747 ("microblaze: Allow > PAGE_SIZE configuration"), was rather nebulous with "can improve > performance on some workloads". > > On PowerPC, the benefits of larger pages are mainly for the hashed > page table code, which I don't think exists anywhere else. Is there any standard benchmark to see if there is really any benefit? Exchanging tbl is quite expensive operation that's why there could be good improvement. But not a problem to remove it for now and get it back when this is properly tested. Thanks, Michal