Replace pthread_rwlock with std::shared_mutex

[rgacogne]

Short description

Closes #10209.

The speed tests result looks good, except perhaps for a small regression in the "RW lock shared" case but since we are talking of 1 usec for 1000 operations, I believe we can live with that.

• master

'getlock-uncontended-test' 0.11 seconds: 112247847.3 runs/s, 0.01 usec/run
'RW lock shared' 0.11 seconds: 107827.9 runs/s, 9.27 usec/run
'RW lock exclusive' 0.11 seconds: 72534.4 runs/s, 13.79 usec/run
'RW lock try exclusive - non-contended' 0.11 seconds: 69176.3 runs/s, 14.46 usec/run
'RW lock try exclusive - contended' 0.11 seconds: 255326.8 runs/s, 3.92 usec/run
'RW lock try shared - non-contended' 0.11 seconds: 107123.5 runs/s, 9.34 usec/run
'RW lock try shared - contended' 0.11 seconds: 255821.4 runs/s, 3.91 usec/run

'getlock-uncontended-test' 0.11 seconds: 113262655.2 runs/s, 0.01 usec/run
'RW lock shared' 0.11 seconds: 108756.1 runs/s, 9.19 usec/run
'RW lock exclusive' 0.11 seconds: 73071.9 runs/s, 13.69 usec/run
'RW lock try exclusive - non-contended' 0.11 seconds: 69429.8 runs/s, 14.40 usec/run
'RW lock try exclusive - contended' 0.11 seconds: 257484.5 runs/s, 3.88 usec/run
'RW lock try shared - non-contended' 0.11 seconds: 108059.3 runs/s, 9.25 usec/run
'RW lock try shared - contended' 0.11 seconds: 257798.9 runs/s, 3.88 usec/run

• PR

'getlock-uncontended-test' 0.11 seconds: 111842329.5 runs/s, 0.01 usec/run
'RW lock shared' 0.11 seconds: 95161.0 runs/s, 10.51 usec/run
'RW lock exclusive' 0.11 seconds: 72660.4 runs/s, 13.76 usec/run
'RW lock try exclusive - non-contended' 0.11 seconds: 71733.0 runs/s, 13.94 usec/run
'RW lock try exclusive - contended' 0.11 seconds: 360459.7 runs/s, 2.77 usec/run
'RW lock try shared - non-contended' 0.11 seconds: 106830.7 runs/s, 9.36 usec/run
'RW lock try shared - contended' 0.11 seconds: 255051.5 runs/s, 3.92 usec/run

'getlock-uncontended-test' 0.11 seconds: 112064700.8 runs/s, 0.01 usec/run
'RW lock shared' 0.11 seconds: 96040.2 runs/s, 10.41 usec/run
'RW lock exclusive' 0.11 seconds: 72596.2 runs/s, 13.77 usec/run
'RW lock try exclusive - non-contended' 0.11 seconds: 71517.1 runs/s, 13.98 usec/run
'RW lock try exclusive - contended' 0.11 seconds: 360546.4 runs/s, 2.77 usec/run
'RW lock try shared - non-contended' 0.11 seconds: 107134.1 runs/s, 9.33 usec/run
'RW lock try shared - contended' 0.11 seconds: 255380.6 runs/s, 3.92 usec/run

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[omoerbeek]

What I always found confusing: to declare a lock object you use ReadWriteLock, but to take a lock is ReadLock or WriteLock. I'd love to rename the latter to TakeReadLock and TakeWriteLock. Or maybe Acquire... ?

Alternatively we could rename ReadWriteLock to ReadWriteLockObject.

[rgacogne]

That feels like a different pull request to me but sure, feel free to do so.

[omoerbeek]

That feels like a different pull request to me but sure, feel free to do so.

Yes, that would be a change in interface while this PR only concerns implementation. I agree a separate PR is better for that part.

[omoerbeek]

I'll test soon to see if linux/clang has the same performance regression as OpenBSD/clang (about 2x slower).

[rgacogne]

What I always found confusing: to declare a lock object you use ReadWriteLock, but to take a lock is ReadLock or WriteLock. I'd love to rename the latter to TakeReadLock and TakeWriteLock. Or maybe Acquire... ?

Perhaps ReadLockHolder and WriteLockHolder?

[omoerbeek]

I think it is clear OpenBSD is the outlier.

On buster using clang-7 using a random laptop with an Intel(R) Core(TM) i5-3320M CPU @ 2.60GHz

master lock.hh

'getlock-uncontended-test' 0.10 seconds: 46332207.3 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 40933.0 runs/s, 24.43 usec/run
'RW lock exclusive' 0.10 seconds: 31021.2 runs/s, 32.24 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 35554.8 runs/s, 28.13 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 156333.8 runs/s, 6.40 usec/run
'RW lock try shared - non-contended' 0.11 seconds: 45011.4 runs/s, 22.22 usec/run
'RW lock try shared - contended' 0.10 seconds: 149328.7 runs/s, 6.70 usec/run

'getlock-uncontended-test' 0.10 seconds: 46323242.3 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 40940.3 runs/s, 24.43 usec/run
'RW lock exclusive' 0.10 seconds: 31007.2 runs/s, 32.25 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 35562.7 runs/s, 28.12 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 156237.3 runs/s, 6.40 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45044.9 runs/s, 22.20 usec/run
'RW lock try shared - contended' 0.10 seconds: 149309.6 runs/s, 6.70 usec/run

PR:

'getlock-uncontended-test' 0.10 seconds: 46330696.6 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 43152.7 runs/s, 23.17 usec/run
'RW lock exclusive' 0.10 seconds: 36010.2 runs/s, 27.77 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 36040.1 runs/s, 27.75 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 252381.8 runs/s, 3.96 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45053.8 runs/s, 22.20 usec/run
'RW lock try shared - contended' 0.10 seconds: 205280.7 runs/s, 4.87 usec/run

'getlock-uncontended-test' 0.10 seconds: 46330866.0 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 43131.5 runs/s, 23.18 usec/run
'RW lock exclusive' 0.10 seconds: 36077.9 runs/s, 27.72 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 36063.9 runs/s, 27.73 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 252517.0 runs/s, 3.96 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45043.7 runs/s, 22.20 usec/run
'RW lock try shared - contended' 0.10 seconds: 205220.1 runs/s, 4.87 usec/run

So here the PR is better. To compare, I also checked with clang-8:
master:

'getlock-uncontended-test' 0.10 seconds: 46332160.1 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 40929.9 runs/s, 24.43 usec/run
'RW lock exclusive' 0.10 seconds: 31201.5 runs/s, 32.05 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 35547.9 runs/s, 28.13 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 149345.5 runs/s, 6.70 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45055.2 runs/s, 22.19 usec/run
'RW lock try shared - contended' 0.10 seconds: 149340.9 runs/s, 6.70 usec/run

'getlock-uncontended-test' 0.10 seconds: 46294863.5 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 40949.5 runs/s, 24.42 usec/run
'RW lock exclusive' 0.10 seconds: 31019.1 runs/s, 32.24 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 35525.7 runs/s, 28.15 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 149294.1 runs/s, 6.70 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45048.0 runs/s, 22.20 usec/run
'RW lock try shared - contended' 0.10 seconds: 149315.0 runs/s, 6.70 usec/run

PR:

'getlock-uncontended-test' 0.10 seconds: 46322617.8 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 43129.5 runs/s, 23.19 usec/run
'RW lock exclusive' 0.10 seconds: 35687.1 runs/s, 28.02 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 35986.0 runs/s, 27.79 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 252474.4 runs/s, 3.96 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45034.9 runs/s, 22.20 usec/run
'RW lock try shared - contended' 0.10 seconds: 193297.2 runs/s, 5.17 usec/run

'getlock-uncontended-test' 0.10 seconds: 46318164.1 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 43153.5 runs/s, 23.17 usec/run
'RW lock exclusive' 0.10 seconds: 35674.4 runs/s, 28.03 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 36030.9 runs/s, 27.75 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 252454.5 runs/s, 3.96 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45055.3 runs/s, 22.19 usec/run
'RW lock try shared - contended' 0.10 seconds: 193222.4 runs/s, 5.18 usec/run

And gcc8.3:

master:

'gettimeofday-test' 0.10 seconds: 51933786.5 runs/s, 0.02 usec/run
'getlock-uncontended-test' 0.10 seconds: 47145391.3 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 43228.0 runs/s, 23.13 usec/run
'RW lock exclusive' 0.10 seconds: 35441.5 runs/s, 28.22 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 36027.0 runs/s, 27.76 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 252328.7 runs/s, 3.96 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45056.3 runs/s, 22.19 usec/run
'RW lock try shared - contended' 0.10 seconds: 234651.4 runs/s, 4.26 usec/run

'getlock-uncontended-test' 0.10 seconds: 47141655.2 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 43223.8 runs/s, 23.14 usec/run
'RW lock exclusive' 0.10 seconds: 35431.7 runs/s, 28.22 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 36049.2 runs/s, 27.74 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 252673.9 runs/s, 3.96 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45064.6 runs/s, 22.19 usec/run
'RW lock try shared - contended' 0.10 seconds: 234650.2 runs/s, 4.26 usec/run

PR:

'getlock-uncontended-test' 0.10 seconds: 47131020.4 runs/s, 0.02 usec/run
'RW lock shared' 0.10 seconds: 43212.5 runs/s, 23.14 usec/run
'RW lock exclusive' 0.10 seconds: 36152.2 runs/s, 27.66 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 36080.3 runs/s, 27.72 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 252531.8 runs/s, 3.96 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45069.4 runs/s, 22.19 usec/run
'RW lock try shared - contended' 0.10 seconds: 252239.7 runs/s, 3.96 usec/run

'RW lock shared' 0.10 seconds: 43159.2 runs/s, 23.17 usec/run
'RW lock exclusive' 0.10 seconds: 35734.9 runs/s, 27.98 usec/run
'RW lock try exclusive - non-contended' 0.10 seconds: 36079.4 runs/s, 27.72 usec/run
'RW lock try exclusive - contended' 0.10 seconds: 252365.9 runs/s, 3.96 usec/run
'RW lock try shared - non-contended' 0.10 seconds: 45016.8 runs/s, 22.21 usec/run
'RW lock try shared - contended' 0.10 seconds: 252562.7 runs/s, 3.96 usec/run

[rgacogne]

I'm merging this PR, we will rename the ReadLock and WriteLock in a different one.