From: Dan Williams <dan.j.williams@intel.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Barret Rhoden <brho@google.com>,
Liran Alon <liran.alon@oracle.com>,
Paolo Bonzini <pbonzini@redhat.com>,
David Hildenbrand <david@redhat.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
linux-nvdimm <linux-nvdimm@lists.01.org>, X86 ML <x86@kernel.org>,
KVM list <kvm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Zeng, Jason" <jason.zeng@intel.com>
Subject: Re: [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files
Date: Tue, 7 Jan 2020 17:39:28 -0800 [thread overview]
Message-ID: <CAPcyv4jW3HTU7mmctL_d+zTS8yT_NLxa5cx_w8nbqVSwBMdSLQ@mail.gmail.com> (raw)
In-Reply-To: <20200108012014.GF16987@linux.intel.com>
On Tue, Jan 7, 2020 at 5:20 PM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> On Tue, Jan 07, 2020 at 02:19:06PM -0500, Barret Rhoden wrote:
> > On 1/7/20 2:05 PM, Sean Christopherson wrote:
> > >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.
>
> Will do. Barring last minute hiccups, the code is ready, just need to
> finish off a few changelogs. Should get it out early tomorrow.
>
> One question that may help avoid some churn: are huge DAX pages not
> tracked as compound pages? The comment from your/this patch is pretty
> unequivocal, but I wanted to double check that they will really return
> false for PageCompound(), as opposed to only returning false for
> PageTransCompoundMap().
PageCompound() returns false.
>
> /*
> * DAX pages do not use compound pages. ...
> */
>
None of the head / tail page infrastructure is set up for dax pages.
They are just independent 'struct page' objects that are
opportunistically mapped by different pte sizes in the dax core.
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prev parent reply other threads:[~2020-01-08 1:39 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 18:22 [PATCH v5 0/2] kvm: Use huge pages for DAX-backed files Barret Rhoden
2019-12-12 18:22 ` [PATCH v5 1/2] mm: make dev_pagemap_mapping_shift() externally visible Barret Rhoden
2019-12-13 17:47 ` Sean Christopherson
2019-12-13 18:13 ` Dan Williams
2019-12-16 17:59 ` Barret Rhoden
2019-12-18 0:18 ` Sean Christopherson
2020-01-15 18:33 ` Paolo Bonzini
2019-12-12 18:22 ` [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files Barret Rhoden
2019-12-12 18:47 ` Liran Alon
2019-12-12 18:49 ` Liran Alon
2019-12-12 19:55 ` Barret Rhoden
2019-12-13 1:07 ` Liran Alon
2019-12-13 14:13 ` Barret Rhoden
2019-12-13 17:19 ` Sean Christopherson
2019-12-13 17:31 ` Liran Alon
2019-12-13 17:50 ` Sean Christopherson
2019-12-13 18:08 ` Liran Alon
2019-12-16 16:05 ` Barret Rhoden
2020-01-07 19:05 ` Sean Christopherson
2020-01-07 19:19 ` Barret Rhoden
2020-01-08 1:20 ` Sean Christopherson
2020-01-08 1:39 ` Dan Williams [this message]
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