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Thu, 21 May 2020 21:06:20 +0000 Date: Thu, 21 May 2020 14:06:16 -0700 From: Roman Gushchin To: Vlastimil Babka CC: Andrew Morton , Johannes Weiner , Michal Hocko , , , , Christoph Lameter Subject: Re: [PATCH v3 04/19] mm: slub: implement SLUB version of obj_to_index() Message-ID: <20200521210616.GA339999@carbon.DHCP.thefacebook.com> References: <20200422204708.2176080-1-guro@fb.com> <20200422204708.2176080-5-guro@fb.com> <0e0616f2-6c5a-8911-7d37-6f2027c2930b@suse.cz> <20200520210040.GC278395@carbon.dhcp.thefacebook.com> <266af2b2-41d0-368c-1896-1a7637389054@suse.cz> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <266af2b2-41d0-368c-1896-1a7637389054@suse.cz> X-ClientProxiedBy: BYAPR05CA0016.namprd05.prod.outlook.com (2603:10b6:a03:c0::29) To BYAPR15MB4136.namprd15.prod.outlook.com (2603:10b6:a03:96::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.DHCP.thefacebook.com (2620:10d:c090:400::5:84a2) by BYAPR05CA0016.namprd05.prod.outlook.com (2603:10b6:a03:c0::29) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3021.11 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: Q0o/0WC4Vr10mXE8W+YD7MN5W0GuqDdCKUt7F9ohpF2uffJDeh2P+yO4RHe/V2Vk+vgGr9CcrRRrDhPEnYIDifQoL6VM8lCFjaz3b4XRuIo1ogzWHktC0Oy6NkPMdpCP5WPIdysiJ2mspuseDWxVblZYLQ/+2AMzpGkUAzI1bJLMo1ESi3CGLTrbhRNHiaFFR4c/gQWigP1uJhKFZ9T+GfwQgMlFFotQ4EdVQ2eln+jhTSG2MA/C8aRpZVLYrXvZbe60S80gavl6DL5b1lJKGS5vzcmyW1IZnjbJtKmkq7Ytifm0CgwOrFoFyCIPneKw/7guQC/SIQb6Tgyk9F6k0ZZc3mBVQl5Lnrzet7tqRhIa2xmh9BLc9h3nfKIacc61emI+EveYVzws1u/DXf90bwwzHf8beKIjya/ITT8Y5bYSL0RqNvxaLC/A1E1gTSvvMpE8l6/y9kmHpyuw5ZYceUgQdUILdtD0SfLO6y+9GGt03fRN5+vet/k3WamIgiV6GkbSc+f5qBXY1X3To0ufSA== X-MS-Exchange-CrossTenant-Network-Message-Id: 1b278c95-3ba6-4bd3-e413-08d7fdcacf24 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 May 2020 21:06:20.0484 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Rabqyd7f1L3uOA7D6acxSpSkmGbb2yin15jnKb8f1wgCC0xz6kW1BFSFuvM1Q3mc X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2310 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.676 definitions=2020-05-21_14:2020-05-21,2020-05-21 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 mlxscore=0 spamscore=0 cotscore=-2147483648 mlxlogscore=750 clxscore=1015 bulkscore=0 adultscore=0 impostorscore=0 suspectscore=1 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005210157 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 21, 2020 at 01:01:38PM +0200, Vlastimil Babka wrote: > On 5/20/20 11:00 PM, Roman Gushchin wrote: > > > > From beeaecdac85c3a395dcfb99944dc8c858b541cbf Mon Sep 17 00:00:00 2001 > > From: Roman Gushchin > > Date: Mon, 29 Jul 2019 18:18:42 -0700 > > Subject: [PATCH v3.2 04/19] mm: slub: implement SLUB version of obj_to_index() > > > > This commit implements SLUB version of the obj_to_index() function, > > which will be required to calculate the offset of obj_cgroup in the > > obj_cgroups vector to store/obtain the objcg ownership data. > > > > To make it faster, let's repeat the SLAB's trick introduced by > > commit 6a2d7a955d8d ("[PATCH] SLAB: use a multiply instead of a > > divide in obj_to_index()") and avoid an expensive division. > > > > Vlastimil Babka noticed, that SLUB does have already a similar > > function called slab_index(), which is defined only if SLUB_DEBUG > > is enabled. The function does a similar math, but with a division, > > and it also takes a page address instead of a page pointer. > > > > Let's remove slab_index() and replace it with the new helper > > __obj_to_index(), which takes a page address. obj_to_index() > > will be a simple wrapper taking a page pointer and passing > > page_address(page) into __obj_to_index(). > > > > Signed-off-by: Roman Gushchin > > Looks good! > > Reviewed-by: Vlastimil Babka Thanks!