On Thu, 2011-05-26 at 19:02 +0300, Pekka Enberg wrote: > On Thu, 26 May 2011, Sasha Levin wrote: > > Adds a rwlock wrapper which like the mutex wrapper makes rwlock calls > > similar to their kernel counterparts. > > > > Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx> > > There's no explanation why a mutex isn't sufficient. The pthread locking > primitives aren't all that great in practice so unless you have some > correctness issue that requires a rwlock or some numbers, I'd prefer you > go for a mutex. I've added some rwlocks because of what Ingo said yesterday about adding/removing devices after the first initialization phase. Take MMIO lock for example: Since we can now run SMP guests, we may have multiple MMIO exits (one from each VCPU thread). Each of those exits leads to searching the MMIO rbtree. We can use a mutex to lock it, but it just means that those threads will be blocked there instead of concurrently searching the MMIO tree which makes the search linear instead of parallel. It's hard to bring 'real' numbers at this stage because the only 'real' device we have which uses MMIO is the VESA driver, and we can't really simulate many VCPUs writing to it :) -- Sasha. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
