Date: Sat, 1 Sep 2018 14:38:43 -0700 From: Linus Torvalds <torvalds@...ux-foundation.org> To: jsteckli@...zon.de Cc: David Woodhouse <dwmw@...zon.co.uk>, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, juerg.haefliger@....com, deepa.srinivasan@...cle.com, Jim Mattson <jmattson@...gle.com>, Andrew Cooper <andrew.cooper3@...rix.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, linux-mm <linux-mm@...ck.org>, Thomas Gleixner <tglx@...utronix.de>, joao.m.martins@...cle.com, pradeep.vincent@...cle.com, Andi Kleen <ak@...ux.intel.com>, Khalid Aziz <khalid.aziz@...cle.com>, kanth.ghatraju@...cle.com, Liran Alon <liran.alon@...cle.com>, Kees Cook <keescook@...gle.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, chris.hyser@...cle.com, Tyler Hicks <tyhicks@...onical.com>, John Haxby <john.haxby@...cle.com>, Jon Masters <jcm@...hat.com> Subject: Re: Redoing eXclusive Page Frame Ownership (XPFO) with isolated CPUs in mind (for KVM to isolate its guests per CPU) On Fri, Aug 31, 2018 at 12:45 AM Julian Stecklina <jsteckli@...zon.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. 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
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