On Wed, Jun 5, 2019 at 6:00 PM Phil Yang <phil.y...@arm.com> wrote: > This patch set added MCS lock library and its unit test. > > The MCS lock (proposed by JOHN M. MELLOR-CRUMMEY and MICHAEL L. SCOTT) > provides > scalability by spinning on a CPU/thread local variable which avoids > expensive > cache bouncings. It provides fairness by maintaining a list of acquirers > and > passing the lock to each CPU/thread in the order they acquired the lock. > > References: > 1. > http://web.mit.edu/6.173/www/currentsemester/readings/R06-scalable-synchronization-1991.pdf > 2. https://lwn.net/Articles/590243/ > > Mirco-benchmarking result: > > ------------------------------------------------------------------------------------------------ > MCS lock | spinlock | ticket > lock > > ------------------------------+--------------------------------+-------------------------------- > Test with lock on 13 cores... | Test with lock on 14 cores... | Test > with lock on 14 cores... > Core [15] Cost Time = 22426 us| Core [14] Cost Time = 47974 us| Core > [14] cost time = 66761 us > Core [16] Cost Time = 22382 us| Core [15] Cost Time = 46979 us| Core > [15] cost time = 66766 us > Core [17] Cost Time = 22294 us| Core [16] Cost Time = 46044 us| Core > [16] cost time = 66761 us > Core [18] Cost Time = 22412 us| Core [17] Cost Time = 28793 us| Core > [17] cost time = 66767 us > Core [19] Cost Time = 22407 us| Core [18] Cost Time = 48349 us| Core > [18] cost time = 66758 us > Core [20] Cost Time = 22436 us| Core [19] Cost Time = 19381 us| Core > [19] cost time = 66766 us > Core [21] Cost Time = 22414 us| Core [20] Cost Time = 47914 us| Core > [20] cost time = 66763 us > Core [22] Cost Time = 22405 us| Core [21] Cost Time = 48333 us| Core > [21] cost time = 66766 us > Core [23] Cost Time = 22435 us| Core [22] Cost Time = 38900 us| Core > [22] cost time = 66749 us > Core [24] Cost Time = 22401 us| Core [23] Cost Time = 45374 us| Core > [23] cost time = 66765 us > Core [25] Cost Time = 22408 us| Core [24] Cost Time = 16121 us| Core > [24] cost time = 66762 us > Core [26] Cost Time = 22380 us| Core [25] Cost Time = 42731 us| Core > [25] cost time = 66768 us > Core [27] Cost Time = 22395 us| Core [26] Cost Time = 29439 us| Core > [26] cost time = 66768 us > | Core [27] Cost Time = 38071 us| Core > [27] cost time = 66767 us > > ------------------------------+--------------------------------+-------------------------------- > Total Cost Time = 291195 us | Total Cost Time = 544403 us | Total > cost time = 934687 us > > ------------------------------------------------------------------------------------------------ >
Had a quick look, interesting. Quick comments: - your numbers are for 13 cores, while the other are for 14, what is the reason? - do we need per architecture header? all I can see is generic code, we might as well directly put rte_mcslock.h in the common/include directory. - could we replace the current spinlock with this approach? is this more expensive than spinlock on lowly contended locks? is there a reason we want to keep all these approaches? we could have now 3 lock implementations. - do we need to write the authors names in full capitalized version? it seems like you are shouting :-) -- David Marchand
