From: Paolo Bonzini <pbonzini@redhat.com>
To: Dan Williams <dan.j.williams@intel.com>, Barret Rhoden <brho@google.com>
Cc: X86 ML <x86@kernel.org>, "Zhang, Yu C" <yu.c.zhang@intel.com>,
KVM list <kvm@vger.kernel.org>,
rkrcmar@redhat.com, linux-nvdimm <linux-nvdimm@lists.01.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
zwisler@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Zhang, Yi Z" <yi.z.zhang@intel.com>
Subject: Re: [RFC PATCH] kvm: Use huge pages for DAX-backed files
Date: Wed, 31 Oct 2018 09:52:04 +0100 [thread overview]
Message-ID: <e00c5f69-f4d7-859c-cbde-0392b0a5195c@redhat.com> (raw)
In-Reply-To: <CAPcyv4gJUjuSKwy7i2wuKR=Vz-AkDrxnGya5qkg7XTFxuXbtzw@mail.gmail.com>
On 29/10/2018 23:25, Dan Williams wrote:
> I'm wondering if we're adding an explicit is_zone_device_page() check
> in this path to determine the page mapping size if that can be a
> replacement for the kvm_is_reserved_pfn() check. In other words, the
> goal of fixing up PageReserved() was to preclude the need for DAX-page
> special casing in KVM, but if we already need add some special casing
> for page size determination, might as well bypass the
> kvm_is_reserved_pfn() dependency as well.
No, please don't. The kvm_is_reserved_pfn() check is for correctness,
the page-size check is for optimization. In theory you could have a
ZONE_DEVICE area that is smaller than 2MB and thus does not use huge pages.
Paolo
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Dan Williams <dan.j.williams@intel.com>, Barret Rhoden <brho@google.com>
Cc: Dave Jiang <dave.jiang@intel.com>,
zwisler@kernel.org, Vishal L Verma <vishal.l.verma@intel.com>,
rkrcmar@redhat.com, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>,
KVM list <kvm@vger.kernel.org>,
"Zhang, Yu C" <yu.c.zhang@intel.com>,
"Zhang, Yi Z" <yi.z.zhang@intel.com>
Subject: Re: [RFC PATCH] kvm: Use huge pages for DAX-backed files
Date: Wed, 31 Oct 2018 09:52:04 +0100 [thread overview]
Message-ID: <e00c5f69-f4d7-859c-cbde-0392b0a5195c@redhat.com> (raw)
In-Reply-To: <CAPcyv4gJUjuSKwy7i2wuKR=Vz-AkDrxnGya5qkg7XTFxuXbtzw@mail.gmail.com>
On 29/10/2018 23:25, Dan Williams wrote:
> I'm wondering if we're adding an explicit is_zone_device_page() check
> in this path to determine the page mapping size if that can be a
> replacement for the kvm_is_reserved_pfn() check. In other words, the
> goal of fixing up PageReserved() was to preclude the need for DAX-page
> special casing in KVM, but if we already need add some special casing
> for page size determination, might as well bypass the
> kvm_is_reserved_pfn() dependency as well.
No, please don't. The kvm_is_reserved_pfn() check is for correctness,
the page-size check is for optimization. In theory you could have a
ZONE_DEVICE area that is smaller than 2MB and thus does not use huge pages.
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Dan Williams
<dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
Barret Rhoden <brho-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: X86 ML <x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
"Zhang,
Yu C" <yu.c.zhang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
KVM list <kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
rkrcmar-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
linux-nvdimm
<linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>,
Linux Kernel Mailing List
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>,
zwisler-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
"Zhang,
Yi Z" <yi.z.zhang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [RFC PATCH] kvm: Use huge pages for DAX-backed files
Date: Wed, 31 Oct 2018 09:52:04 +0100 [thread overview]
Message-ID: <e00c5f69-f4d7-859c-cbde-0392b0a5195c@redhat.com> (raw)
In-Reply-To: <CAPcyv4gJUjuSKwy7i2wuKR=Vz-AkDrxnGya5qkg7XTFxuXbtzw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On 29/10/2018 23:25, Dan Williams wrote:
> I'm wondering if we're adding an explicit is_zone_device_page() check
> in this path to determine the page mapping size if that can be a
> replacement for the kvm_is_reserved_pfn() check. In other words, the
> goal of fixing up PageReserved() was to preclude the need for DAX-page
> special casing in KVM, but if we already need add some special casing
> for page size determination, might as well bypass the
> kvm_is_reserved_pfn() dependency as well.
No, please don't. The kvm_is_reserved_pfn() check is for correctness,
the page-size check is for optimization. In theory you could have a
ZONE_DEVICE area that is smaller than 2MB and thus does not use huge pages.
Paolo
next prev parent reply other threads:[~2018-10-31 8:52 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-29 21:07 [RFC PATCH] kvm: Use huge pages for DAX-backed files Barret Rhoden
2018-10-29 21:07 ` Barret Rhoden
2018-10-29 22:25 ` Dan Williams
2018-10-29 22:25 ` Dan Williams
2018-10-29 22:25 ` Dan Williams
[not found] ` <CAPcyv4gJUjuSKwy7i2wuKR=Vz-AkDrxnGya5qkg7XTFxuXbtzw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-10-30 0:28 ` Barret Rhoden
2018-10-30 0:28 ` Barret Rhoden
2018-10-30 3:10 ` Dan Williams
2018-10-30 3:10 ` Dan Williams
[not found] ` <CAPcyv4gQztHrJ3--rhU4ZpaZyyqdqE0=gx50CRArHKiXwfYC+A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-10-30 19:45 ` Barret Rhoden
2018-10-30 19:45 ` Barret Rhoden
2018-10-31 8:49 ` Paolo Bonzini
2018-10-31 8:49 ` Paolo Bonzini
2018-11-02 20:32 ` Barret Rhoden
2018-11-06 10:19 ` Paolo Bonzini
[not found] ` <876d5a71-8dda-4728-5329-4e169777ba4a-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-11-06 16:22 ` Barret Rhoden
2018-11-06 16:22 ` Barret Rhoden
2018-10-31 3:05 ` Yu Zhang
2018-10-31 3:05 ` Yu Zhang
2018-10-31 3:05 ` Yu Zhang
2018-10-31 8:52 ` Paolo Bonzini [this message]
2018-10-31 8:52 ` Paolo Bonzini
2018-10-31 8:52 ` Paolo Bonzini
2018-10-31 21:16 ` Dan Williams
2018-10-31 21:16 ` Dan Williams
2018-10-31 21:16 ` Dan Williams
2018-11-06 10:22 ` Paolo Bonzini
[not found] ` <20181029210716.212159-1-brho-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2018-11-06 21:05 ` Barret Rhoden
2018-11-06 21:05 ` Barret Rhoden
2018-11-06 21:16 ` Paolo Bonzini
2018-11-06 21:16 ` Paolo Bonzini
2018-11-06 21:17 ` Barret Rhoden
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=e00c5f69-f4d7-859c-cbde-0392b0a5195c@redhat.com \
--to=pbonzini@redhat.com \
--cc=bp@alien8.de \
--cc=brho@google.com \
--cc=dan.j.williams@intel.com \
--cc=hpa@zytor.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nvdimm@lists.01.org \
--cc=mingo@redhat.com \
--cc=rkrcmar@redhat.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
--cc=yi.z.zhang@intel.com \
--cc=yu.c.zhang@intel.com \
--cc=zwisler@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.