Re: [PATCH v9 10/15] x86/sgx: Add EPC reclamation in cgroup try_charge()

From: "Huang, Kai" <kai.huang@intel.com>
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>
Subject: Re: [PATCH v9 10/15] x86/sgx: Add EPC reclamation in cgroup try_charge()
Date: Tue, 27 Feb 2024 11:46:02 +1300	[thread overview]
Message-ID: <022a37e1-7d51-4d64-bb07-91bce848186c@intel.com> (raw)
In-Reply-To: <ddec5892-b748-425e-acea-4757bdeecb8b@intel.com>

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.