netdev - Re: [PATCH 06/18] x86, barrier: stop speculation for failed access

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Date:   Sun, 7 Jan 2018 21:12:11 +0100
From:   Willy Tarreau <w@....eu>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Dan Williams <dan.j.williams@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Network Development <netdev@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 06/18] x86, barrier: stop speculation for failed access_ok

On Sun, Jan 07, 2018 at 11:47:07AM -0800, Linus Torvalds wrote:
> And the whole "normal people won't even notice" is pure garbage too.
> Don't spread that bullshit when you see actual normal people
> complaining.
> 
> Performance matters. A *LOT*.

Linus, no need to explain that to me, I'm precisely trying to see how
to disable PTI for a specific process because I face up to 45% loss in
certain circumstances, making it a no-go. But while a few of us have
very specific workloads emphasizing this impact, others have very
different ones and will not notice. For example my laptop did boot
pretty fine and I didn't notice anything until I fire a network
benchmark.

Willy