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From: Linus Torvalds <torvalds@linux-foundation.org>
To: jsteckli@amazon.de
Cc: David Woodhouse <dwmw@amazon.co.uk>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	juerg.haefliger@hpe.com, deepa.srinivasan@oracle.com,
	Jim Mattson <jmattson@google.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	linux-mm <linux-mm@kvack.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	joao.m.martins@oracle.com, pradeep.vincent@oracle.com,
	Andi Kleen <ak@linux.intel.com>,
	Khalid Aziz <khalid.aziz@oracle.com>,
	kanth.ghatraju@oracle.com, Liran Alon <liran.alon@oracle.com>,
	Kees Cook <keescook@google.com>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	chris.hyser@oracle.com, Tyler Hicks <tyhicks@canonical.com>,
	John Haxby <john.haxby@oracle.com>, Jon Masters <jcm@redhat.com>
Subject: Re: Redoing eXclusive Page Frame Ownership (XPFO) with isolated CPUs in mind (for KVM to isolate its guests per CPU)
Date: Sat, 1 Sep 2018 14:38:43 -0700	[thread overview]
Message-ID: <CA+55aFzHj_GNZWG4K2oDu4DPP9sZdTZ9PY7sBxGB6WoN9g8d=A@mail.gmail.com> (raw)
In-Reply-To: <ciirm8a7p3alos.fsf@u54ee758033e858cfa736.ant.amazon.com>

On Fri, Aug 31, 2018 at 12:45 AM Julian Stecklina <jsteckli@amazon.de> wrote:
>
> I've been spending some cycles on the XPFO patch set this week. For the
> patch set as it was posted for v4.13, the performance overhead of
> compiling a Linux kernel is ~40% on x86_64[1]. The overhead comes almost
> completely from TLB flushing. If we can live with stale TLB entries
> allowing temporary access (which I think is reasonable), we can remove
> all TLB flushing (on x86). This reduces the overhead to 2-3% for
> kernel compile.

I have to say, even 2-3% for a kernel compile sounds absolutely horrendous.

Kernel bullds are 90% user space at least for me, so a 2-3% slowdown
from a kernel is not some small unnoticeable thing.

           Linus

  parent reply	other threads:[~2018-09-01 21:39 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-20 21:25 Redoing eXclusive Page Frame Ownership (XPFO) with isolated CPUs in mind (for KVM to isolate its guests per CPU) Konrad Rzeszutek Wilk
2018-08-20 21:48 ` Linus Torvalds
     [not found]   ` <1534801939.10027.24.camel@amazon.co.uk>
2018-08-20 22:18     ` Kees Cook
2018-08-20 22:27     ` Linus Torvalds
2018-08-20 22:35       ` Tycho Andersen
2018-08-20 22:59         ` Dave Hansen
2018-08-20 23:14           ` David Woodhouse
2018-08-20 23:26             ` Dave Hansen
2018-08-20 23:38               ` Linus Torvalds
2018-08-21  9:57       ` David Woodhouse
2018-08-21 14:01         ` Liran Alon
2018-08-21 14:22           ` David Woodhouse
2018-08-21 23:04             ` Liran Alon
2018-08-30 16:00       ` Julian Stecklina
2018-08-31 15:26         ` Tycho Andersen
2018-09-01 21:38         ` Linus Torvalds [this message]
2018-09-03 14:51           ` Julian Stecklina
2018-09-12 15:37             ` Julian Stecklina
2018-09-13  6:11               ` Juerg Haefliger
2018-09-17 10:01                 ` Julian Stecklina
2018-09-17 10:19                   ` Tycho Andersen
2018-09-17 13:27                   ` Christoph Hellwig
2018-09-14 17:06               ` Khalid Aziz
2018-09-17  9:51                 ` Julian Stecklina
2018-09-18 23:00                   ` Khalid Aziz
2018-09-24 14:45                     ` Stecklina, Julian
2018-10-15  8:07                       ` Khalid Aziz
2018-10-24 11:00                         ` Khalid Aziz
2018-10-24 15:00                           ` Tycho Andersen
2018-09-03 15:26           ` Andi Kleen
2018-09-04  9:37             ` Julian Stecklina
     [not found]           ` <CACfEFw_h5uup-anKZwfBcWMJB7gHxb9NEPTRSUAY0+t11RiQbg@mail.gmail.com>
2018-09-03 15:36             ` Andi Kleen
2018-09-07 21:30         ` Khalid Aziz
2018-08-31  8:43     ` James Bottomley
2018-09-19  1:03     ` Balbir Singh
2018-09-19 15:43       ` Jonathan Adams
2018-09-23  2:33         ` Balbir Singh
2018-09-25 14:12           ` Stecklina, Julian

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