On 05/23/2010 06:51 PM, Michael S. Tsirkin wrote: >> >>> So locked version seems to be faster than unlocked, >>> and share/unshare not to matter? >>> >>> >> May be due to the processor using the LOCK operation as a hint to >> reserve the cacheline for a bit. >> > Maybe we should use atomics on index then? >
This should only be helpful if you access the cacheline several times in a row. That's not the case in virtio (or here). I think the problem is that LOCKSHARE and SHARE are not symmetric, so they can't be directly compared. > OK, after adding mb in code patch will be sent separately, > the test works for my workstation. locked is still fastest, > unshared sometimes shows wins and sometimes loses over shared. > > [r...@qus19 ~]# ./cachebounce share 0 1 > CPU 0: share cacheline: 6638521 usec > CPU 1: share cacheline: 6638478 usec > 66 ns? nice. > [r...@qus19 ~]# ./cachebounce share 0 2 > CPU 0: share cacheline: 14529198 usec > CPU 2: share cacheline: 14529156 usec > 140 ns, not too bad. I hope I'm not misinterpreting the results. -- error compiling committee.c: too many arguments to function _______________________________________________ Virtualization mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/virtualization
