linux-kernel - [PATCH 0/3] x86: enlightenment for ticket spinlocks

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Message-Id: <4B62A39D020000780002CA80@vpn.id2.novell.com>
Date:	Fri, 29 Jan 2010 08:00:13 +0000
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 0/3] x86: enlightenment for ticket spinlocks

With the pv-ops based spinlocks reportedly having measurable overhead
on native execution, and with them also not easily fit (at least) fully
virtualized Xen guests, this patch series introduces a replacement
mechanism based on alternative instruction patching, and then uses it
for fully virtualized Xen guests. While coded to be orthogonal to
pv-ops, it really isn't, and it shouldn't be difficult to make pv-ops guests
use this in place of pv-ops spin locks.

The only additional overhead this introduces for native execution is
the writing of the owning CPU in the lock acquire paths. If this is
considered a problem, even that code could be eliminated for native
execution (by further alternative instruction patching).

(1) base implementation
(2) Xen implementation
(3) [optional] eliminate on NOPs in unlock path (introduced in (1))

Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

View attachment "linux-2.6.33-rc5-virt-spinlocks-xen.patch" of type "text/plain" (12621 bytes)

View attachment "linux-2.6.33-rc5-virt-spinlocks-base.patch" of type "text/plain" (17612 bytes)

View attachment "linux-2.6.33-rc5-virt-spinlocks-no-nop.patch" of type "text/plain" (5126 bytes)