For spinlock and read-write locks, both *_unlock() and *_unlock_irq()
functions are inlined if !PREEMPT. Whereas the *_unlock_bh() and
*unlock_irqrestore() are not inlined as that will increase the size
of the kernel binary.
Given the fact that the PV qspinlock unlock call is a callee-saved
function pointer, the unlock function is essentially a leaf function
if !PREEMPT is true under all circumstances. Inlining it will enable
the compiler to do much better optimization around the the unlock
call sites. Similarly for the read-write locks.
To unleash this additional performance, all these unlock functions
are now inlined for x86-64 kernel where kernel size is usually less
of a concern. For 32-bit kernel, it is assumed that the focus will
be a bit more on kernel size optimization and so those functions are
not inlined.
With 4.9.6 kernel source and gcc 4.8.5-11 compiler, the text size
of the base vmlinux binary increased from 8527918 bytes to 8462235
bytes. That was an increase of 0.78%.
On a 2-socket 24-core 48-thread system, the performance of the AIM7
high_systime workload (1000 users) increased from 209818.43 jobs/min
to 213333.33 jobs/min. That was an increase of 1.68%.
Signed-off-by: Waiman Long <long...@redhat.com>
---
arch/x86/Kconfig | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7b6fd68..a0fbed7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -23,6 +23,12 @@ config X86_64
depends on 64BIT
# Options that are inherently 64-bit kernel only:
select ARCH_HAS_GIGANTIC_PAGE
+ select ARCH_INLINE_READ_UNLOCK_BH if !PREEMPT
+ select ARCH_INLINE_READ_UNLOCK_IRQRESTORE if !PREEMPT
+ select ARCH_INLINE_SPIN_UNLOCK_BH if !PREEMPT
+ select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPT
+ select ARCH_INLINE_WRITE_UNLOCK_BH if !PREEMPT
+ select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE if !PREEMPT
select ARCH_SUPPORTS_INT128
select ARCH_USE_CMPXCHG_LOCKREF
select HAVE_ARCH_SOFT_DIRTY
--
1.8.3.1
