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>,
Dave Jiang <dave.jiang@intel.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.
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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