Messages in this thread | | | Subject | [PATCH 0/2] rwsem: performance enhancements for systems with many cores | From | Tim Chen <> | Date | Fri, 21 Jun 2013 16:51:31 -0700 |
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In this patchset, we introduce two optimizations to read write semaphore. The first one reduces cache bouncing of the sem->count field by doing a pre-read of the sem->count and avoid cmpxchg if possible. The second patch introduces similar optimistic spining logic in the mutex code for the writer lock acquisition of rw-sem.
Combining the two patches, in testing by Davidlohr Bueso on aim7 workloads on 8 socket 80 cores system, he saw improvements of alltests (+14.5%), custom (+17%), disk (+11%), high_systime (+5%), shared (+15%) and short (+4%), most of them after around 500 users when i_mmap was implemented as rwsem.
Feedbacks on the effectiveness of these tweaks on other workloads will be appreciated.
Alex Shi (1): rwsem: check the lock before cpmxchg in down_write_trylock and rwsem_do_wake
Tim Chen (1): rwsem: do optimistic spinning for writer lock acquisition
Makefile | 2 +- include/asm-generic/rwsem.h | 8 +- include/linux/rwsem.h | 3 + init/Kconfig | 9 +++ kernel/rwsem.c | 29 +++++++- lib/rwsem.c | 169 ++++++++++++++++++++++++++++++++++++++----- 6 files changed, 195 insertions(+), 25 deletions(-)
-- 1.7.4.4
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