linux-kernel - Re: [PATCH v5 12/18] x86/sgx: Add EPC OOM path to forcefully reclaim EPC

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Message-ID: <op.2c0nt109wjvjmi@hhuan26-mobl.amr.corp.intel.com>
Date:   Wed, 18 Oct 2023 10:26:15 -0500
From:   "Haitao Huang" <haitao.huang@...ux.intel.com>
To:     Michal Koutný <mkoutny@...e.com>,
        "Dave Hansen" <dave.hansen@...el.com>
Cc:     "Christopherson,, Sean" <seanjc@...gle.com>,
        "Huang, Kai" <kai.huang@...el.com>,
        "Zhang, Bo" <zhanb@...rosoft.com>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        "yangjie@...rosoft.com" <yangjie@...rosoft.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "Li, Zhiquan1" <zhiquan1.li@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "tj@...nel.org" <tj@...nel.org>,
        "anakrish@...rosoft.com" <anakrish@...rosoft.com>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "mikko.ylinen@...ux.intel.com" <mikko.ylinen@...ux.intel.com>,
        "Mehta, Sohil" <sohil.mehta@...el.com>,
        "bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
        "kristen@...ux.intel.com" <kristen@...ux.intel.com>
Subject: Re: [PATCH v5 12/18] x86/sgx: Add EPC OOM path to forcefully reclaim
 EPC

On Wed, 18 Oct 2023 08:55:12 -0500, Dave Hansen <dave.hansen@...el.com>  
wrote:

> On 10/17/23 21:37, Haitao Huang wrote:
>> Yes we can introduce misc.reclaim to give user a knob to forcefully
>> reducing usage if that is really needed in real usage. The semantics
>> would make force-kill VMs explicit to user.
>
> Do any other controllers do something like this?  It seems odd.

Maybe not in sense of killing something. My understanding memory.reclaim  
does not necessarily invoke the OOM killer. But what I really intend to  
say is we can have a separate knob for user to express the need for  
reducing the current usage explicitly and keep "misc.max' non-preemptive  
semantics intact. When we implement that new knob, then we can define what  
kind of reclaim for that. Depending on vEPC implementation, it may or may  
not involve killing VMs. But at least that semantics will be explicit for  
user.

Thanks
Haitao