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Tue, 26 May 2020 18:50:37 +0000 Date: Tue, 26 May 2020 11:50:27 -0700 From: Roman Gushchin To: Vlastimil Babka CC: Andrew Morton , Johannes Weiner , Michal Hocko , , , Subject: Re: [PATCH v3 15/19] mm: memcg/slab: deprecate slab_root_caches Message-ID: <20200526185027.GD377498@carbon.DHCP.thefacebook.com> References: <20200422204708.2176080-1-guro@fb.com> <20200422204708.2176080-16-guro@fb.com> <613dda66-4fa6-1820-50c4-c7b28235e687@suse.cz> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <613dda66-4fa6-1820-50c4-c7b28235e687@suse.cz> X-ClientProxiedBy: BY3PR05CA0027.namprd05.prod.outlook.com (2603:10b6:a03:254::32) To SN6PR1501MB4141.namprd15.prod.outlook.com (2603:10b6:805:e3::14) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.DHCP.thefacebook.com (2620:10d:c090:400::5:fbe3) by BY3PR05CA0027.namprd05.prod.outlook.com (2603:10b6:a03:254::32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3045.8 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: KEZns79DQf2qCq3d5Kdu9LcRONNKaVaRLW+uPn1uKWKHxHaH4iAsj3nnHMLDs9Zokhms6ICIBOkrFXDcqCGo4jI2b0+xfa4QRVzbVCQc5vVWk+rfvBSAgoNtxaBmaEUeYMVYMDHBKLyFxowKL5VTQC0BSGXHBW6Rokb83jlUTkddJDCFpGoGK4dOGsnm0KfzyIUxQODzKO/UPlz9hla3C38zajiD11icX0s63kxW6Ui4eKxXlNWb84SraCxcVulks8bdFYuSLYQPLiCfmseXkfJn0vTYNCmleAKJmfVL5ptlvz9CySLL/KchXQ+yndJv6uC+UNWCpFF6Enc52QakSggxZfudJaw9h9yK0Q6Nuwqd/CZZJ8zMcBgWtzKbI//04AgMSenriJ8A7xXh8sQONYmAewjB09oIOjGcYqPH5aEVC4265/pRKVW4PUEQngRXjWioxmpZTIe6tVvkuUv0C/xXFuJKiP2t0lgQrrus+xbSpw98IL3+3BcR1B43z71i+XRvTDbQ4gNVgsYH8rcMHA== X-MS-Exchange-CrossTenant-Network-Message-Id: 1f453e38-15cc-428a-9f47-08d801a5adcd X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 May 2020 18:50:37.1789 (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: EFx/NbV0uvdypTedtVE2RjJ2CMe8A2CySFO4V3HfIrAJEc+yM+jkaNw2huiL1hhA X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR1501MB2175 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-05-26_02:2020-05-26,2020-05-26 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 mlxlogscore=759 suspectscore=2 priorityscore=1501 cotscore=-2147483648 adultscore=0 malwarescore=0 phishscore=0 bulkscore=0 impostorscore=0 mlxscore=0 clxscore=1015 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005260145 X-FB-Internal: deliver 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 Tue, May 26, 2020 at 12:52:24PM +0200, Vlastimil Babka wrote: > On 4/22/20 10:47 PM, Roman Gushchin wrote: > > Currently there are two lists of kmem_caches: > > 1) slab_caches, which contains all kmem_caches, > > 2) slab_root_caches, which contains only root kmem_caches. > > > > And there is some preprocessor magic to have a single list > > if CONFIG_MEMCG_KMEM isn't enabled. > > > > It was required earlier because the number of non-root kmem_caches > > was proportional to the number of memory cgroups and could reach > > really big values. Now, when it cannot exceed the number of root > > kmem_caches, there is really no reason to maintain two lists. > > > > We never iterate over the slab_root_caches list on any hot paths, > > so it's perfectly fine to iterate over slab_caches and filter out > > non-root kmem_caches. > > > > It allows to remove a lot of config-dependent code and two pointers > > from the kmem_cache structure. > > > > Signed-off-by: Roman Gushchin > > Reviewed-by: Vlastimil Babka Thanks! > > > @@ -1148,11 +1126,12 @@ static void cache_show(struct kmem_cache *s, struct seq_file *m) > > > > static int slab_show(struct seq_file *m, void *p) > > { > > - struct kmem_cache *s = list_entry(p, struct kmem_cache, root_caches_node); > > + struct kmem_cache *s = list_entry(p, struct kmem_cache, list); > > > > - if (p == slab_root_caches.next) > > + if (p == slab_caches.next) > > print_slabinfo_header(m); > > - cache_show(s, m); > > + if (is_root_cache(s)) > > + cache_show(s, m); > > If there wasn't patch 17/19 we could just remove this condition and have > /proc/slabinfo contain the -memcg variants? Sure, it's an option too. But because it's a user facing option, I'd keep it as it is now at least until everything will settle down a bit. Thanks!