From 442302820356977237e32a76a211e7942255003a Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Mon, 8 Sep 2014 08:20:43 +0200 Subject: [PATCH] s390/spinlock: optimize spin_unlock code Use a memory barrier + store sequence instead of a load + compare and swap sequence to unlock a spinlock and an rw lock. For the spinlock case this saves us two memory reads and a not needed cpu serialization after the compare and swap instruction stored the new value. The kernel size (performance_defconfig) gets reduced by ~14k. Average execution time of a tight inlined spin_unlock loop drops from 5.8ns to 0.7ns on a zEC12 machine. An artificial stress test case where several counters are protected with a single spinlock and which are only incremented while holding the spinlock shows ~30% improvement on a 4 cpu machine. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- Reading git-format-patch failed