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

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Date: Mon, 26 Feb 2024 06:04:54 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: "Huang, Kai" <kai.huang@...el.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>,
 "haitao.huang@...ux.intel.com" <haitao.huang@...ux.intel.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 03:36, Huang, Kai wrote:
>> In case of overcomitting, even if we always reclaim from the same cgroup  
>> for each fault, one group may still interfere the other: e.g., consider an  
>> extreme case in that group A used up almost all EPC at the time group B  
>> has a fault, B has to fail allocation and kill enclaves.
> If the admin allows group A to use almost all EPC, to me it's fair to say he/she
> doesn't want to run anything inside B at all and it is acceptable enclaves in B
> to be killed.

Folks, I'm having a really hard time following this thread.  It sounds
like there's disagreement about when to do system-wide reclaim.  Could
someone remind me of the choices that we have?  (A proposed patch would
go a _long_ way to helping me understand)

Also, what does the core mm memcg code do?

Last, what is the simplest (least amount of code) thing that the SGX
cgroup controller could implement here?