linux-kernel - Re: [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files

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Date:   Tue, 7 Jan 2020 14:19:06 -0500
From:   Barret Rhoden <brho@...gle.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Liran Alon <liran.alon@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        linux-nvdimm@...ts.01.org, x86@...nel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, jason.zeng@...el.com
Subject: Re: [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files

Hi -

On 1/7/20 2:05 PM, Sean Christopherson wrote:
> On Mon, Dec 16, 2019 at 11:05:26AM -0500, Barret Rhoden wrote:
>> On 12/13/19 12:19 PM, Sean Christopherson wrote:
>>> Teaching thp_adjust() how to handle 1GB wouldn't be a bad thing.  It's
>>> unlikely THP itself will support 1GB pages any time soon, but having the
>>> logic there wouldn't hurt anything.
>>>
>>
>> Cool.  This was my main concern - I didn't want to break THP.
>>
>> I'll rework the series based on all of your comments.
> 
> Hopefully you haven't put too much effort into the rework, because I want
> to commandeer the proposed changes and use them as the basis for a more
> aggressive overhaul of KVM's hugepage handling.  Ironically, there's a bug
> in KVM's THP handling that I _think_ can be avoided by using the DAX
> approach of walking the host PTEs.
> 
> I'm in the process of testing, hopefully I'll get a series sent out later
> today.  If not, I should at least be able to provide an update.

Nice timing.  I was just about to get back to this, so I haven't put any 
time in yet.  =)

Please CC me, and I'll try your patches out on my end.

Thanks,

Barret