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Re: [RFC PATCH] getcpu_cache system call: caching current CPU number (x86)
- From: Andy Lutomirski <luto at amacapital dot net>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: Ben Maurer <bmaurer at fb dot com>, Ingo Molnar <mingo at redhat dot com>, libc-alpha <libc-alpha at sourceware dot org>, linux-api <linux-api at vger dot kernel dot org>, Andrew Morton <akpm at linux-foundation dot org>, OndÅej BÃlka <neleai at seznam dot cz>, rostedt <rostedt at goodmis dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>, Josh Triplett <josh at joshtriplett dot org>, Lai Jiangshan <laijs at cn dot fujitsu dot com>, Paul Turner <pjt at google dot com>, Andrew Hunter <ahh at google dot com>, Peter Zijlstra <peterz at infradead dot org>
- Date: Mon, 20 Jul 2015 08:31:28 -0700
- Subject: Re: [RFC PATCH] getcpu_cache system call: caching current CPU number (x86)
- Authentication-results: sourceware.org; auth=none
- References: <1436724386-30909-1-git-send-email-mathieu dot desnoyers at efficios dot com> <5CDDBDF2D36D9F43B9F5E99003F6A0D48D5F39C6 at PRN-MBX02-1 dot TheFacebook dot com> <587954201 dot 31 dot 1436808992876 dot JavaMail dot zimbra at efficios dot com> <5CDDBDF2D36D9F43B9F5E99003F6A0D48D5F5DA0 at PRN-MBX02-1 dot TheFacebook dot com> <549319255 dot 383 dot 1437070088597 dot JavaMail dot zimbra at efficios dot com> <CALCETrWEKE=mow3vVh7C4r8CuGy_d5VOEz7KkpijuR5cpBfFtg at mail dot gmail dot com> <CA+55aFz-VBnEKh0SPKgu8xV5=Zb+=6odybVUDoOYOknshbcFJA at mail dot gmail dot com> <20150717232836 dot GA13604 at domone> <CALCETrVY=kjeA_4pazy3BL+ekfcV6WHKw8e3z-LBxx_uP1bw2Q at mail dot gmail dot com> <55ACB2DC dot 5010503 at redhat dot com>
On Jul 20, 2015 1:35 AM, "Florian Weimer" <fweimer@redhat.com> wrote:
>
> On 07/18/2015 01:33 AM, Andy Lutomirski wrote:
>
> > I think the API should be "set gsbase to x + y*(cpu number)". On
> > x86_64, userspace just allocates a big swath of virtual space and
> > populates it as needed.
>
> This will break WINE and similar applications which use %gs today.
Presumably WINE could just opt not to use this facility, just like
WINE will have to opt out of whatever the enterprise people who want
WRGSBASE were thinking of doing with it.
--Andy