Received-SPF: pass (google.com: domain of linux-kernel+bounces-61088-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Date: Mon, 12 Feb 2024 12:10:38 +0800
From: "Jan Kratochvil (Azul)" <jkratochvil@azul.com>
To: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, containers@lists.osdl.org,
	Waiman Long <longman@redhat.com>
Subject: [PATCH v2] Port hierarchical_{memory,swap}_limit cgroup1->cgroup2
Message-ID: <ZcmaPqZ9HzoN0GFM@host1.jankratochvil.net>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/2.2.12 (2023-09-09)
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0:
	=?us-ascii?Q?S0NPgBbkTK4CLtXIZZPaqlk9IhE5++Q0YCmtGlM7iIuOAuIIRniMIPyuvORa?=
 =?us-ascii?Q?iyCdUV2I341rEVWpWELw9vB8MkNfaC2pBDfTUcW17NmMcnlkE2O4k+RlmcOx?=
 =?us-ascii?Q?aSKk4nslfcFc/W2/Z5cZxrErbR93xYTLW80EBJJs9WBTTvdARcAJAtQaP9p2?=
 =?us-ascii?Q?UPn+CMcX6Noy43pE8HtSdlCgGnN4HVPaEr13H43GkKK91z9coOQnGkamande?=
 =?us-ascii?Q?pnv7TuRqy90339Q90euc4LJhyHx+boljvIlO/SN8lZ7OLgHVzSD/8IXhrYFX?=
 =?us-ascii?Q?k1vzqkLXrHG391l+WtmC/hm3JJkeG/84Zbn2SV2qbfdidz1nyX2eFtWJfU91?=
 =?us-ascii?Q?EvcMHAl+T2f1J5FAszUCLqKmwIvM2bKLSI3VA1rKLPZYY++UeTlKkfYLWkAk?=
 =?us-ascii?Q?74gudCMqcoK0CWKcQFXNHmicYRzsFeNd4sucD+FoGJBhrzAYG9M7VhC1uy3o?=
 =?us-ascii?Q?4Fq1OirKv57+mhQdsdxKk+1kgNSOfud5McIrvTHvbEjY7b3lUNwyPwCng1yN?=
 =?us-ascii?Q?f/BzbfxInWo17ZNG9a1r21yfBqvjSwqqmU6YYAz0PKI4aUHjloQ4itUXdHzC?=
 =?us-ascii?Q?KUQm0KCkmbyOG3Pc9ydg81WJQ5YicTivbruhosaP7R+ipD+tV6QHjb3s/qV2?=
 =?us-ascii?Q?HvXsYk3dHsf5dhak0+oYr+NHxGN+MDya4P4asY6Vu+SetDWl0afnoxWsmNh6?=
 =?us-ascii?Q?UMkhH234gcdYj31TJX6XpPkLcW7CXh3Xh/mYWyPizJ8+JVDc8F691yG5kBBx?=
 =?us-ascii?Q?PRoL6OB2dytED51NvOCQl57v84TdoEIy+6ihqb/v+bh3MmNUTr4PAHjPJQmh?=
 =?us-ascii?Q?7fkGPgWPdjeVGAjj/gCbdfnSWovUHyUotpby30t/5CoIgMdskSCBhSHNxEMh?=
 =?us-ascii?Q?NS55XTpcYpnG8HDXisRqIP93hUmbfXFrt4MiKInq+YmWtn5a/awS5Qb3XyXA?=
 =?us-ascii?Q?a56fgudtDKOQdrUHUX8UzmYmwUQ5vim/J2fFyzXNSl1jA03mx2DQ0hBnly9I?=
 =?us-ascii?Q?RPiuY2d/j0SiFgQUfPCR0n5aKs46TLXEdvNdIcyBA7EO9sIHQ1LEg7nNijkZ?=
 =?us-ascii?Q?iMQhiZh9QWgnAXQh4KoAqG0xyOvU8CCi4vxtT2xq1fg82jZbQPHZMSbYiPqu?=
 =?us-ascii?Q?NJ9vcKSj8LgJ6FUSef55akXUWZVQjs3xejeGeNgigNZS83D7n9vxxSbafGCH?=
 =?us-ascii?Q?fCi0UHZ/XUVYLwO5++646LUSESZpETudWvR3pkzbBdg+b2hbQ2lMrxfR+qwb?=
 =?us-ascii?Q?DG5/0xyNF0wCKHsJA9Rq3HfsYiMiqjoaAUWvfxO2yrWLfIKZiTCrV2o9rRWN?=
 =?us-ascii?Q?fDcw8JoKiBgTc+vMeq2KDIWsjV5HReFdu86q20ixmoBrHZ2rWbRFTx2WRvyw?=
 =?us-ascii?Q?Sr0+jNFwiOryuG5Q/ccQsvsiLtw1qCSpJSS9p/IvecYsfZHO5l/urehNWMXM?=
 =?us-ascii?Q?RMUdj8/L+WSF7YaStCcTfLKb3br9EM0LkeSmLKqcnznY9IL722fW0IArXJmH?=
 =?us-ascii?Q?TnEOP4l9fD3utAO58LE1/n1KGq+MtilqxP3RUGo+8QBwmcfim5c10FmirzWu?=
 =?us-ascii?Q?oh+EaMTxFVs59ChvvsfJCxMbCb3umFb8ti1nWYzm0y7wCIOzWs8bXztpI0Bz?=
 =?us-ascii?Q?AA=3D=3D?=
X-OriginatorOrg: azul.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 1ca32c8c-f966-483b-2ab5-08dc2b809534
X-MS-Exchange-CrossTenant-AuthSource: CH2PR11MB4342.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Feb 2024 04:10:44.1288
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: c480eb31-2b17-43d7-b4c7-9bcb20cc4bf2
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: y6Iid77jxILCwwFEg+YWqNg4e3b5Ev/fvYhk6NwEzML0wLGux5970HdMuTV6+uY6G9v7jHZ9SUzdfhvUzTDhKw==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR11MB6859

Hello,

cgroup1 (by function memcg1_stat_format) already contains two lines
	hierarchical_memory_limit %llu
	hierarchical_memsw_limit %llu

which are useful for userland to easily and performance-wise find out the
effective cgroup limits being applied. Otherwise userland has to
open+read+close the file "memory.max" and/or "memory.swap.max" in multiple
parent directories of a nested cgroup.

For cgroup1 it was implemented by:
	memcg: show real limit under hierarchy mode
	https://github.com/torvalds/linux/commit/fee7b548e6f2bd4bfd03a1a45d3afd593de7d5e9
	Date:   Wed Jan 7 18:08:26 2009 -0800

But for cgroup2 it has been missing so far, this is just a copy-paste of the
cgroup1 code while changing s/memsw/swap/ as that is what cgroup1 vs. cgroup2
tracks. I have added it to the end of "memory.stat" to prevent possible
compatibility problems with existing code parsing that file.


Jan Kratochvil


Signed-off-by: Jan Kratochvil (Azul) <jkratochvil@azul.com>

 mm/memcontrol.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 46d8d0211..2631dd810 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1636,6 +1636,8 @@ static inline unsigned long memcg_page_state_local_output(
 static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
 {
 	int i;
+	unsigned long memory, swap;
+	struct mem_cgroup *mi;
 
 	/*
 	 * Provide statistics on the state of the memory subsystem as
@@ -1682,6 +1684,17 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
 			       memcg_events(memcg, memcg_vm_event_stat[i]));
 	}
 
+	/* Hierarchical information */
+	memory = swap = PAGE_COUNTER_MAX;
+	for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) {
+		memory = min(memory, READ_ONCE(mi->memory.max));
+		swap = min(swap, READ_ONCE(mi->swap.max));
+	}
+	seq_buf_printf(s, "hierarchical_memory_limit %llu\n",
+		       (u64)memory * PAGE_SIZE);
+	seq_buf_printf(s, "hierarchical_swap_limit %llu\n",
+		       (u64)swap * PAGE_SIZE);
+
 	/* The above should easily fit into one page */
 	WARN_ON_ONCE(seq_buf_has_overflowed(s));
 }