On Wed, Jun 5, 2019 at 6:00 PM Phil Yang
<phil.y...@arm.com<mailto: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 :-)
[Honnappa] IMO, writing full names is a cultural thing? I do not see any harm.
But, I do think, we do not need to capitalize everything.
--
David Marchand
[Honnappa] This mail is appearing as HTML, would be good to change to text
mode. It is much easier to add inline comments.
