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Message-ID: <022a37e1-7d51-4d64-bb07-91bce848186c@intel.com>
Date: Tue, 27 Feb 2024 11:46:02 +1300
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Subject: Re: [PATCH v9 10/15] x86/sgx: Add EPC reclamation in cgroup
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To: Dave Hansen <dave.hansen@intel.com>, Haitao Huang
	<haitao.huang@linux.intel.com>, "tj@kernel.org" <tj@kernel.org>,
	"jarkko@kernel.org" <jarkko@kernel.org>, "x86@kernel.org" <x86@kernel.org>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>, "hpa@zytor.com"
	<hpa@zytor.com>, "mingo@redhat.com" <mingo@redhat.com>,
	"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>, "mkoutny@suse.com"
	<mkoutny@suse.com>, "Mehta, Sohil" <sohil.mehta@intel.com>,
	"linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>, "bp@alien8.de" <bp@alien8.de>
CC: "mikko.ylinen@linux.intel.com" <mikko.ylinen@linux.intel.com>,
	"seanjc@google.com" <seanjc@google.com>, "anakrish@microsoft.com"
	<anakrish@microsoft.com>, "Zhang, Bo" <zhanb@microsoft.com>,
	"kristen@linux.intel.com" <kristen@linux.intel.com>, "yangjie@microsoft.com"
	<yangjie@microsoft.com>, "Li, Zhiquan1" <zhiquan1.li@intel.com>,
	"chrisyan@microsoft.com" <chrisyan@microsoft.com>
References: <20240205210638.157741-1-haitao.huang@linux.intel.com>
 <20240205210638.157741-11-haitao.huang@linux.intel.com>
 <c5d03171473821ebc9cb79e3dad4d1bf0074e674.camel@intel.com>
 <op.2jjzaqdwwjvjmi@hhuan26-mobl.amr.corp.intel.com>
 <4db8493b-35a2-474f-997c-5e6ac1b8bd11@intel.com>
 <op.2jkfeezjwjvjmi@hhuan26-mobl.amr.corp.intel.com>
 <c913193c0560c4372d2fdb31e9edb28bcb419f50.camel@intel.com>
 <op.2jlti6g9wjvjmi@hhuan26-mobl.amr.corp.intel.com>
 <7b53e155-2622-4acb-b7c9-d22e623e4cb3@intel.com>
 <op.2jqdjjd8wjvjmi@hhuan26-mobl.amr.corp.intel.com>
 <48faaea8b24f032baa6a858a2909a5b4ace769c6.camel@intel.com>
 <d9b0df06-da68-4729-8aac-2a77e890e152@intel.com>
 <op.2jrquskiwjvjmi@hhuan26-mobl.amr.corp.intel.com>
 <3f4c6d12-7e0f-44ca-920e-ec219904e0aa@intel.com>
 <b4c7e743-55d7-4a76-baeb-871b0e8cf394@intel.com>
 <ddec5892-b748-425e-acea-4757bdeecb8b@intel.com>
From: "Huang, Kai" <kai.huang@intel.com>
In-Reply-To: <ddec5892-b748-425e-acea-4757bdeecb8b@intel.com>
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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.