linux-kernel - Re: [PATCH RFCv2 0/9] kvm/arm64: Support Async Page Fault

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Message-ID: <ae0f32fa338969d25dc3da56292e35ed@kernel.org>
Date:   Wed, 27 May 2020 08:48:27 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Gavin Shan <gshan@...hat.com>
Cc:     Mark Rutland <mark.rutland@....com>, kvmarm@...ts.cs.columbia.edu,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, will@...nel.org, catalin.marinas@....com,
        james.morse@....com, suzuki.poulose@....com, drjones@...hat.com,
        eric.auger@...hat.com, aarcange@...hat.com, shan.gavin@...il.com
Subject: Re: [PATCH RFCv2 0/9] kvm/arm64: Support Async Page Fault

On 2020-05-27 03:39, Gavin Shan wrote:
> Hi Mark,

[...]

>> Can you run tests with a real workload? For example, a kernel build
>> inside the VM?
>> 
> 
> Yeah, I agree it's far from a realistic workload. However, it's the 
> test case
> which was suggested when async page fault was proposed from day one, 
> according
> to the following document. On the page#34, you can see the benchmark, 
> which is
> similar to what we're doing.
> 
> https://www.linux-kvm.org/images/a/ac/2010-forum-Async-page-faults.pdf

My own question is whether this even makes any sense 10 years later.

The HW has massively changed, and this adds a whole lot of complexity
to both the hypervisor and the guest. It also plays very ugly games
with the exception model, which doesn't give me the warm fuzzy feeling
that it's going to be great.

> Ok. I will test with the workload to build kernel or another better one 
> to
> represent the case.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...