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| author | Heiko Carstens | 2014-09-08 08:20:43 +0200 |
|---|---|---|
| committer | Martin Schwidefsky | 2014-09-09 08:53:30 +0200 |
| commit | 442302820356977237e32a76a211e7942255003a (patch) | |
| tree | caf9d4d00753beab556f28f4f4cfac3d7f8b73e9 /drivers/s390/crypto | |
| parent | s390/ftrace: optimize mcount code (diff) | |
| download | kernel-qcow2-linux-442302820356977237e32a76a211e7942255003a.tar.gz kernel-qcow2-linux-442302820356977237e32a76a211e7942255003a.tar.xz kernel-qcow2-linux-442302820356977237e32a76a211e7942255003a.zip | |
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 <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'drivers/s390/crypto')
0 files changed, 0 insertions, 0 deletions