kernel_optimize_test/arch/unicore32
Christian Borntraeger 79ab11cdb9 locking/core: Introduce cpu_relax_yield()
For spinning loops people do often use barrier() or cpu_relax().
For most architectures cpu_relax and barrier are the same, but on
some architectures cpu_relax can add some latency.
For example on power,sparc64 and arc, cpu_relax can shift the CPU
towards other hardware threads in an SMT environment.
On s390 cpu_relax does even more, it uses an hypercall to the
hypervisor to give up the timeslice.
In contrast to the SMT yielding this can result in larger latencies.
In some places this latency is unwanted, so another variant
"cpu_relax_lowlatency" was introduced. Before this is used in more
and more places, lets revert the logic and provide a cpu_relax_yield
that can be called in places where yielding is more important than
latency. By default this is the same as cpu_relax on all architectures.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Noam Camus <noamc@ezchip.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1477386195-32736-2-git-send-email-borntraeger@de.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-11-16 10:15:09 +01:00
..
boot kbuild: drop redundant "PHONY += FORCE" 2016-04-20 10:38:40 +02:00
configs unicore32: use the new LED disk activity trigger 2016-06-27 08:58:42 +02:00
include locking/core: Introduce cpu_relax_yield() 2016-11-16 10:15:09 +01:00
kernel unicore32: use simpler API for random address requests 2016-10-11 15:06:32 -07:00
lib unicore32: fix build error for find bitops 2011-11-15 17:13:14 +08:00
mm dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
.gitignore
Kconfig unicore: do away with ARCH_REQUIRE_GPIOLIB 2016-06-08 09:55:46 +02:00
Kconfig.debug arch: consolidate CONFIG_STRICT_DEVM in lib/Kconfig.debug 2016-01-09 06:30:49 -08:00
Makefile unicore32: Use generic init_task 2012-05-05 13:00:26 +02:00