From 9ea4c380066fbe23fe0da7f4abfabc444f2467f4 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 19 Nov 2013 16:13:38 +0100 Subject: locking: Optimize lock_bh functions Currently all _bh_ lock functions do two preempt_count operations: local_bh_disable(); preempt_disable(); and for the unlock: preempt_enable_no_resched(); local_bh_enable(); Since its a waste of perfectly good cycles to modify the same variable twice when you can do it in one go; use the new __local_bh_{dis,en}able_ip() functions that allow us to provide a preempt_count value to add/sub. So define SOFTIRQ_LOCK_OFFSET as the offset a _bh_ lock needs to add/sub to be done in one go. As a bonus it gets rid of the preempt_enable_no_resched() usage. This reduces a 1000 loops of: spin_lock_bh(&bh_lock); spin_unlock_bh(&bh_lock); from 53596 cycles to 51995 cycles. I didn't do enough measurements to say for absolute sure that the result is significant but the the few runs I did for each suggest it is so. Reviewed-by: Thomas Gleixner Signed-off-by: Peter Zijlstra Cc: jacob.jun.pan@linux.intel.com Cc: Mike Galbraith Cc: hpa@zytor.com Cc: Arjan van de Ven Cc: lenb@kernel.org Cc: rjw@rjwysocki.net Cc: rui.zhang@intel.com Cc: Linus Torvalds Cc: Andrew Morton Link: http://lkml.kernel.org/r/20131119151338.GF3694@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- include/linux/spinlock_api_up.h | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) (limited to 'include/linux/spinlock_api_up.h') diff --git a/include/linux/spinlock_api_up.h b/include/linux/spinlock_api_up.h index af1f47229e70..d0d188861ad6 100644 --- a/include/linux/spinlock_api_up.h +++ b/include/linux/spinlock_api_up.h @@ -24,11 +24,14 @@ * flags straight, to suppress compiler warnings of unused lock * variables, and to add the proper checker annotations: */ +#define ___LOCK(lock) \ + do { __acquire(lock); (void)(lock); } while (0) + #define __LOCK(lock) \ - do { preempt_disable(); __acquire(lock); (void)(lock); } while (0) + do { preempt_disable(); ___LOCK(lock); } while (0) #define __LOCK_BH(lock) \ - do { local_bh_disable(); __LOCK(lock); } while (0) + do { __local_bh_disable_ip(_THIS_IP_, SOFTIRQ_LOCK_OFFSET); ___LOCK(lock); } while (0) #define __LOCK_IRQ(lock) \ do { local_irq_disable(); __LOCK(lock); } while (0) @@ -36,12 +39,15 @@ #define __LOCK_IRQSAVE(lock, flags) \ do { local_irq_save(flags); __LOCK(lock); } while (0) +#define ___UNLOCK(lock) \ + do { __release(lock); (void)(lock); } while (0) + #define __UNLOCK(lock) \ - do { preempt_enable(); __release(lock); (void)(lock); } while (0) + do { preempt_enable(); ___UNLOCK(lock); } while (0) #define __UNLOCK_BH(lock) \ - do { preempt_enable_no_resched(); local_bh_enable(); \ - __release(lock); (void)(lock); } while (0) + do { __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_LOCK_OFFSET); \ + ___UNLOCK(lock); } while (0) #define __UNLOCK_IRQ(lock) \ do { local_irq_enable(); __UNLOCK(lock); } while (0) -- cgit