Re: [PATCH v5 3/8] qspinlock, x86: Add x86 specific optimization for 2 contending tasks

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Mar 04, 2014 at 05:58:00PM +0100, Peter Zijlstra wrote:
>  2:  17141.324050        2:    620.185930        2:    618.737681

So I forgot that AMD has compute units that share L2:

root@interlagos:~/spinlocks# export LOCK=./ticket ; ($LOCK 0 1 ; $LOCK 0 2) | awk '/^total/ { print $2 }'
982.938839
1325.702905
root@interlagos:~/spinlocks# export LOCK=./qspinlock-pending-opt2 ; ($LOCK 0 1 ; $LOCK 0 2) | awk '/^total/ { print $2 }'
630.684313
999.119087
root@interlagos:~/spinlocks# export LOCK=./waiman ; ($LOCK 0 1 ; $LOCK 0 2) | awk '/^total/ { print $2 }'
620.562791
1644.700639


Doing the same for Intel SMT, which shares L1:


root@westmere:~/spinlocks# export LOCK=./ticket ; ($LOCK 0 12 ; $LOCK 0 1) | awk '/^total/ { print $2 }'
45.765302
1292.721827
root@westmere:~/spinlocks# export LOCK=./qspinlock-pending-opt2 ; ($LOCK 0 12 ; $LOCK 0 1) | awk '/^total/ { print $2 }'
54.536890
1260.467527
root@westmere:~/spinlocks# export LOCK=./waiman ; ($LOCK 0 12 ; $LOCK 0 1) | awk '/^total/ { print $2 }'
65.944794
1230.522895