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sysv sem has two lock modes: One with per-semaphore locks, one lock mode with a single global lock for the whole array. When switching from the per-semaphore locks to the global lock, all per-semaphore locks must be scanned for ongoing operations. The patch adds a hysteresis for switching from the global lock to the per semaphore locks. This reduces how often the per-semaphore locks must be scanned. Compared to the initial patch, this is a simplified solution: Setting USE_GLOBAL_LOCK_HYSTERESIS to 1 restores the current behavior. In theory, a workload with exactly 10 simple sops and then one complex op now scales a bit worse, but this is pure theory: If there is concurrency, the it won't be exactly 10:1:10:1:10:1:... If there is no concurrency, then there is no need for scalability. Link: http://lkml.kernel.org/r/1476851896-3590-3-git-send-email-manfred@colorfullife.com Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: H. Peter Anvin <hpa@zytor.com> Cc: <1vier1@web.de> Cc: kernel test robot <xiaolong.ye@intel.com> Cc: <felixh@informatik.uni-bremen.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| clocksource | ||
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| keys | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
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| ras | ||
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| soc | ||
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| target | ||
| trace | ||
| uapi | ||
| video | ||
| xen | ||
| Kbuild | ||