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From: Christopher Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>
To: Mathieu Desnoyers
	<mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
Cc: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	"Paul E. McKenney"
	<paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
	Boqun Feng <boqun.feng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>,
	Dave Watson <davejwatson-b10kYP2dOMg@public.gmane.org>,
	linux-kernel
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-api <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>,
	Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
	Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
	Andrew Hunter <ahh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>,
	Ben Maurer <bmaurer-b10kYP2dOMg@public.gmane.org>,
	rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>,
	Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>,
	Linus Torvalds
	<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>
Subject: Re: [RFC PATCH for 4.16 02/21] rseq: Introduce restartable sequences system call (v12)
Date: Fri, 15 Dec 2017 11:13:00 -0600 (CST)	[thread overview]
Message-ID: <alpine.DEB.2.20.1712151103050.26844@nuc-kabylake> (raw)
In-Reply-To: <729438855.35910.1513356742518.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>

On Fri, 15 Dec 2017, Mathieu Desnoyers wrote:

> Another aspect that worries me is applications using the gs segment selector
> for other purposes. Suddenly reserving the gs segment selector for use by a
> library like glibc may lead to incompatibilities with applications already
> using it.

fs/gs seems to be reserved for thread local storage. So it would
be shared in user space like the corresponding cpu segment register in
kernel space where multiple subsystems share %gs.

The same can be done in user space. Ulrich Drepper has a writeup on this

https://www.akkadia.org/drepper/tls.pdf

Savings in execution time could come about because there would not be the
need to determine the address of the processor specific memory area in
each restartable sequence and there would be memory free of contention for
such a sequence in order f.e. to realize fast counters.

  parent reply	other threads:[~2017-12-15 17:13 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-14 16:13 [RFC PATCH for 4.16 00/21] Restartable sequences and CPU op vector Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 01/21] uapi headers: Provide types_32_64.h Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 02/21] rseq: Introduce restartable sequences system call (v12) Mathieu Desnoyers
2017-12-14 16:44   ` Christopher Lameter
2017-12-14 18:12     ` Mathieu Desnoyers
     [not found]       ` <12046460.34426.1513275177081.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-12-14 18:50         ` Christopher Lameter
2017-12-14 19:24           ` Mathieu Desnoyers
2017-12-14 21:14             ` Christopher Lameter
2017-12-14 21:20               ` Peter Zijlstra
2017-12-15 15:05                 ` Christopher Lameter
2017-12-15 16:52                   ` Mathieu Desnoyers
     [not found]                     ` <729438855.35910.1513356742518.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-12-15 17:13                       ` Christopher Lameter [this message]
2017-12-14 19:48           ` Peter Zijlstra
2017-12-14 19:57             ` Mathieu Desnoyers
     [not found]               ` <1772818221.34575.1513281428902.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-12-14 20:09                 ` Peter Zijlstra
2017-12-14 16:13 ` [RFC PATCH for 4.16 03/21] arm: Add restartable sequences support Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 04/21] arm: Wire up restartable sequences system call Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 05/21] x86: Add support for restartable sequences Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 06/21] x86: Wire up restartable sequence system call Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 08/21] powerpc: Wire up restartable sequences " Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 09/21] sched: Implement push_task_to_cpu Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 10/21] cpu_opv: Provide cpu_opv system call (v5) Mathieu Desnoyers
     [not found]   ` <20171214161403.30643-11-mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2018-02-12 15:49     ` Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 11/21] x86: Wire up cpu_opv system call Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 12/21] powerpc: " Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 14/21] selftests: lib.mk: Introduce OVERRIDE_TARGETS Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 15/21] cpu_opv: selftests: Implement selftests (v6) Mathieu Desnoyers
2017-12-14 16:13 ` [RFC PATCH for 4.16 16/21] rseq: selftests: Provide rseq library (v5) Mathieu Desnoyers
     [not found] ` <20171214161403.30643-1-mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-12-14 16:13   ` [RFC PATCH for 4.16 07/21] powerpc: Add support for restartable sequences Mathieu Desnoyers
2017-12-14 16:13   ` [RFC PATCH for 4.16 13/21] arm: Wire up cpu_opv system call Mathieu Desnoyers
2017-12-14 16:13   ` [RFC PATCH for 4.16 17/21] rseq: selftests: Provide percpu_op API Mathieu Desnoyers
2017-12-14 16:14 ` [RFC PATCH for 4.16 18/21] rseq: selftests: Provide basic test Mathieu Desnoyers
2017-12-14 16:14 ` [RFC PATCH for 4.16 19/21] rseq: selftests: Provide basic percpu ops test Mathieu Desnoyers
2017-12-14 16:14 ` [RFC PATCH for 4.16 20/21] rseq: selftests: Provide parametrized tests Mathieu Desnoyers
2017-12-14 16:14 ` [RFC PATCH for 4.16 21/21] rseq: selftests: Provide Makefile, scripts, gitignore Mathieu Desnoyers

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