• Peter Zijlstra (Intel)'s avatar
    locking/pvqspinlock, x86: Implement the paravirt qspinlock call patching · f233f7f1
    Peter Zijlstra (Intel) authored
    We use the regular paravirt call patching to switch between:
    
      native_queued_spin_lock_slowpath()	__pv_queued_spin_lock_slowpath()
      native_queued_spin_unlock()		__pv_queued_spin_unlock()
    
    We use a callee saved call for the unlock function which reduces the
    i-cache footprint and allows 'inlining' of SPIN_UNLOCK functions
    again.
    
    We further optimize the unlock path by patching the direct call with a
    "movb $0,%arg1" if we are indeed using the native unlock code. This
    makes the unlock code almost as fast as the !PARAVIRT case.
    
    This significantly lowers the overhead of having
    CONFIG_PARAVIRT_SPINLOCKS enabled, even for native code.
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Signed-off-by: default avatarWaiman Long <Waiman.Long@hp.com>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Daniel J Blueman <daniel@numascale.com>
    Cc: David Vrabel <david.vrabel@citrix.com>
    Cc: Douglas Hatch <doug.hatch@hp.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Scott J Norton <scott.norton@hp.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: virtualization@lists.linux-foundation.org
    Cc: xen-devel@lists.xenproject.org
    Link: http://lkml.kernel.org/r/1429901803-29771-10-git-send-email-Waiman.Long@hp.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    f233f7f1
qspinlock.h 1.43 KB