linux-kernel - Re: [RFC 00/13] x86/mm: PCID and INVPCID

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Message-ID: <CA+55aFxpGj2koqmcFF9JWzBeheF9473Ka516shwbuhfjVpgxrg@mail.gmail.com>
Date:	Fri, 8 Jan 2016 15:31:03 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Brian Gerst <brgerst@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [RFC 00/13] x86/mm: PCID and INVPCID

On Fri, Jan 8, 2016 at 3:15 PM, Andy Lutomirski <luto@...nel.org> wrote:
>
> Please play around and suggest (and run?) good benchmarks.  It seems
> to save around 100ns on cross-process context switches for me.

Interesting. There was reportedly (I never saw it) a test-patch to use
pcids inside of Intel a couple of years ago, and it never got outside
because it didn't make a difference.

Either things have changed (newer hardware with more pcids perhaps?)
or you did a better job at it.

              Linus