From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>,
Linus Torvalds <torvalds@linux-foundation.com>,
Zachary Amsden <zach@vmware.com>,
Xen-devel <xen-devel@lists.xensource.com>,
Andi Kleen <ak@suse.de>, lkml <linux-kernel@vger.kernel.org>,
Chris Wright <chrisw@sous-sol.org>,
Ian Pratt <ian.pratt@xensource.com>,
Andrew Morton <akpm@linux-foundation.com>,
Ulrich Drepper <drepper@redhat.com>,
Roland McGrath <roland@redhat.com>,
Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Subject: Re: [Xen-devel] [patch 17/44] Add nosegneg capability to the vsyscall page notes
Date: Mon, 16 Jul 2007 18:04:54 -0700 [thread overview]
Message-ID: <469C15B6.8070002@goop.org> (raw)
In-Reply-To: <1184633155.5955.29.camel@localhost.localdomain>
Rusty Russell wrote:
> On Mon, 2007-07-16 at 16:15 -0700, Jeremy Fitzhardinge wrote:
>
>> plain text document attachment (xen-vsyscall-note.patch)
>> Add the "nosegneg" fake capabilty to the vsyscall page notes. This is
>> used by the runtime linker to select a glibc version which then
>> disables negative-offset accesses to the thread-local segment via
>> %gs. These accesses require emulation in Xen (because segments are
>> truncated to protect the hypervisor address space) and avoiding them
>> provides a measurable performance boost.
>>
>
> Hmm, this is still unconditional? Not that it causes any measurable
> slowdown when enabled, but ISTR discussing making this dynamic...
Played with it for a bit, but it's fairly fiddly. Didn't seem like it
was worth the complexity.
J
next prev parent reply other threads:[~2007-07-17 1:06 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20070716231536.937393000@xensource.com>
[not found] ` <20070716232912.409821000@xensource.com>
2007-07-17 0:41 ` [Xen-devel] [patch 03/44] usermodehelper: split setup from execution Rusty Russell
2007-07-17 0:57 ` Jeremy Fitzhardinge
[not found] ` <20070716232914.029797000@xensource.com>
2007-07-17 0:45 ` [Xen-devel] [patch 17/44] Add nosegneg capability to the vsyscall page notes Rusty Russell
2007-07-17 1:04 ` Jeremy Fitzhardinge [this message]
[not found] ` <20070716232916.472694000@xensource.com>
2007-07-17 1:07 ` [patch 37/44] xen: add virtual network device driver Jeff Garzik
2007-07-17 8:45 ` Stephen Hemminger
2007-07-17 14:28 ` Jeremy Fitzhardinge
2007-07-17 23:45 ` Rusty Russell
2007-07-18 0:40 ` Jeremy Fitzhardinge
[not found] ` <20070716232915.672717000@xensource.com>
2007-10-30 9:10 ` [Xen-devel] [patch 30/44] xen: Add support for preemption tgh
2007-10-30 17:25 ` Jeremy Fitzhardinge
2007-10-31 1:23 ` tgh
2007-10-31 1:38 ` Jeremy Fitzhardinge
2007-10-31 6:11 ` tgh
2007-10-31 15:07 ` Jeremy Fitzhardinge
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