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Thu, 18 Jun 2020 19:54:14 +0000 Date: Thu, 18 Jun 2020 12:54:09 -0700 From: Roman Gushchin To: Vlastimil Babka CC: Andrew Morton , Christoph Lameter , Johannes Weiner , Michal Hocko , Shakeel Butt , , , , Kees Cook Subject: Re: [PATCH v6 17/19] mm: memcg/slab: use a single set of kmem_caches for all allocations Message-ID: <20200618195409.GC110603@carbon.dhcp.thefacebook.com> References: <20200608230654.828134-1-guro@fb.com> <20200608230654.828134-18-guro@fb.com> <20200617163528.a4477749b172c387e01c3996@linux-foundation.org> <20200618003515.GB24694@carbon.DHCP.thefacebook.com> <36879e8d-dca7-caf9-71d6-918474ace53e@suse.cz> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <36879e8d-dca7-caf9-71d6-918474ace53e@suse.cz> X-ClientProxiedBy: SN4PR0501CA0146.namprd05.prod.outlook.com (2603:10b6:803:2c::24) 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::5:632d) by SN4PR0501CA0146.namprd05.prod.outlook.com (2603:10b6:803:2c::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3131.13 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: ea33e633-b0e7-40bf-1349-08d813c160a9 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Jun 2020 19:54:14.5946 (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: XEhuiRdUR8Rrep9mepmQOhhHuNoVb2yOeCYL/lRBTwzWKoWQMFiE1H8WdVOrAagM X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2934 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-06-18_15:2020-06-18,2020-06-18 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=2 clxscore=1015 mlxscore=0 spamscore=0 priorityscore=1501 lowpriorityscore=0 phishscore=0 mlxlogscore=898 adultscore=0 impostorscore=0 malwarescore=0 cotscore=-2147483648 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006180151 X-FB-Internal: deliver X-Rspamd-Queue-Id: BE2C518140D60 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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 Thu, Jun 18, 2020 at 09:33:08AM +0200, Vlastimil Babka wrote: > On 6/18/20 2:35 AM, Roman Gushchin wrote: > > On Wed, Jun 17, 2020 at 04:35:28PM -0700, Andrew Morton wrote: > >> On Mon, 8 Jun 2020 16:06:52 -0700 Roman Gushchin wrote: > >> > >> > Instead of having two sets of kmem_caches: one for system-wide and > >> > non-accounted allocations and the second one shared by all accounted > >> > allocations, we can use just one. > >> > > >> > The idea is simple: space for obj_cgroup metadata can be allocated > >> > on demand and filled only for accounted allocations. > >> > > >> > It allows to remove a bunch of code which is required to handle > >> > kmem_cache clones for accounted allocations. There is no more need > >> > to create them, accumulate statistics, propagate attributes, etc. > >> > It's a quite significant simplification. > >> > > >> > Also, because the total number of slab_caches is reduced almost twice > >> > (not all kmem_caches have a memcg clone), some additional memory > >> > savings are expected. On my devvm it additionally saves about 3.5% > >> > of slab memory. > >> > > >> > >> This ran afoul of Vlastimil's "mm, slab/slub: move and improve > >> cache_from_obj()" > >> (http://lkml.kernel.org/r/20200610163135.17364-10-vbabka@suse.cz). I > >> resolved things as below. Not too sure about slab.c's > >> cache_from_obj()... > > > > It can actually be as simple as: > > static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x) > > { > > return s; > > } > > > > But I wonder if we need it at all, or maybe we wanna rename it to > > something like obj_check_kmem_cache(void *obj, struct kmem_cache *s), > > because it has now only debug purposes. > > > > Let me and Vlastimil figure it out and send a follow-up patch. > > Your version is definitely correct. > > Well, Kees wants to restore the common version of cache_from_obj() [1] for SLAB > hardening. > > To prevent all that back and forth churn entering git history, I think the best > is for me to send a -fix to my patch that is functionally same while keeping the > common function, and then this your patch should only have a minor conflict and > Kees can rebase his patches on top to become much smaller? Sounds good to me! Thanks!