linux-kernel - Re: [PATCH v9 10/15] x86/sgx: Add EPC reclamation in cgroup try

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Date: Mon, 26 Feb 2024 14:38:32 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: "Huang, Kai" <kai.huang@...el.com>,
 Haitao Huang <haitao.huang@...ux.intel.com>, "tj@...nel.org"
 <tj@...nel.org>, "jarkko@...nel.org" <jarkko@...nel.org>,
 "x86@...nel.org" <x86@...nel.org>,
 "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
 "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
 "hpa@...or.com" <hpa@...or.com>, "mingo@...hat.com" <mingo@...hat.com>,
 "tim.c.chen@...ux.intel.com" <tim.c.chen@...ux.intel.com>,
 "mkoutny@...e.com" <mkoutny@...e.com>, "Mehta, Sohil"
 <sohil.mehta@...el.com>,
 "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "tglx@...utronix.de" <tglx@...utronix.de>, "bp@...en8.de" <bp@...en8.de>
Cc: "mikko.ylinen@...ux.intel.com" <mikko.ylinen@...ux.intel.com>,
 "seanjc@...gle.com" <seanjc@...gle.com>,
 "anakrish@...rosoft.com" <anakrish@...rosoft.com>,
 "Zhang, Bo" <zhanb@...rosoft.com>,
 "kristen@...ux.intel.com" <kristen@...ux.intel.com>,
 "yangjie@...rosoft.com" <yangjie@...rosoft.com>,
 "Li, Zhiquan1" <zhiquan1.li@...el.com>,
 "chrisyan@...rosoft.com" <chrisyan@...rosoft.com>
Subject: Re: [PATCH v9 10/15] x86/sgx: Add EPC reclamation in cgroup
 try_charge()

On 2/26/24 14:34, Huang, Kai wrote:
> So I am trying to get the actual downside of doing per-cgroup reclaim or
> the full reason that we choose global reclaim.

Take the most extreme example:

	while (hit_global_sgx_limit())
		reclaim_from_this(cgroup);

You eventually end up with all of 'cgroup's pages gone and handed out to
other users on the system who stole them all.  Other users might cause
you to go over the global limit.  *They* should be paying part of the
cost, not just you and your cgroup.