On 08/27/2009 06:54 PM, Marcelo Tosatti wrote:
perf report shows heavy overhead from down/up of slots_lock. Attempted to remove slots_lock by having vcpus stop on a synchronization point, but this introduced further complexity (a vcpu can be scheduled out before reaching the synchronization point, and can sched back in at points which are slots_lock protected, etc). This patch changes vcpu_enter_guest to conditionally release/acquire slots_lock in case a vcpu state bit is set. vmexit performance improves by 5-10% on UP guest.
Sorry, it looks pretty complex. Have you considered using srcu? It seems to me down/up_read() can be replaced by srcu_read_lock/unlock(), and after proper conversion of memslots and io_bus to rcu_assign_pointer(), we can just add synchronize_srcu() immediately after changing stuff (of course mmu_lock still needs to be held when updating slots).
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