On Fri, 2013-06-21 at 16:51 -0700, Tim Chen wrote: > 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. Tim, I was really hoping to send all this in one big bundle. I was doing some further testing (enabling hyperthreading and some Oracle runs), fortunately everything looks ok and we are getting actual improvements on large boxes. That said, how about I send you my i_mmap rwsem patchset for a v2 of this patchset? Thanks, Davidlohr > > > 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(-) > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>