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

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Date: Tue, 27 Feb 2024 11:46:02 +1300
From: "Huang, Kai" <kai.huang@...el.com>
To: Dave Hansen <dave.hansen@...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 27/02/2024 11:38 am, Dave Hansen wrote:
> 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.

Yeah likely we will need another layer of logic to decide when to do 
global reclaim.  I agree that is downside and is unnecessary for this 
patchset.

Thanks for the comments.