From: Jan Beulich on 29 Jan 2010 03:30 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(a)novell.com> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge(a)citrix.com>
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