Message-ID: <bc370c39-d8c1-9371-2345-cf255ced9a1b@intel.com>
Date:   Tue, 11 Jan 2022 07:43:35 -0800
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Subject: Re: [PATCH v2 1/2] x86/sgx: Add accounting for tracking overcommit
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To:     Haitao Huang <haitao.huang@linux.intel.com>,
        linux-sgx@vger.kernel.org, Jarkko Sakkinen <jarkko@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Kristen Carlson Accardi <kristen@linux.intel.com>
Cc:     linux-kernel@vger.kernel.org
References: <20220107181618.6597-1-kristen@linux.intel.com>
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 <3b169fde457f28e086c49c8a3b8d81ac539cfb59.camel@linux.intel.com>
 <op.1ft4sin7wjvjmi@hhuan26-mobl1.mshome.net>
From:   Dave Hansen <dave.hansen@intel.com>
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On 1/11/22 06:20, Haitao Huang wrote:
> If the system has a ton of RAM but limited EPC, I think it makes sense 
> to allow more EPC swapping, can we do min(0.5*RAM, 2*EPC)?
> I suppose if the system is used for heavy enclave load, user would be 
> willing to at least use half of RAM.

If I have 100GB of RAM and 100MB of EPC, can I really *meaningfully* run 
50GB of enclaves?  In that case, if everything was swapped out evenly, I 
would only have a 499/500 chance that a given page reference would fault.

This isn't about a "heavy enclave load".  If there is *that* much 
swapped-out enclave memory, will an enclave even make meaningful forward 
progress?