Messages in this thread | | | Date | Wed, 04 Jan 2012 19:16:59 +0200 | From | Avi Kivity <> | Subject | Re: [RFC PATCH 0/4] Gang scheduling in CFS |
| |
On 01/04/2012 06:47 PM, Rik van Riel wrote: >> So it looks like the default is optimal, at least wrt the cases you >> tested and your test workload. > > > It depends on the workload. > > I believe ebizzy synchronously bounces messages around between > userland threads, and may benefit from lower latency preemption > and re-scheduling. > > Workloads like AMQP do asynchronous messaging, and are likely > to benefit from having a lower number of switches. > > I do not know which kind of workload is more prevalent. > > Another worry with gang scheduling is scalability. One of > the reasons Linux scales well to larger systems is that a > lot of things are done CPU local, without communicating > things with other CPUs. Making the scheduling algorithm > system-global has the potential to add in a lot of overhead. > > Likewise, removing the ability to migrate workloads to idle > CPUs is likely to hurt a lot of real world workloads. > > Benchmarks don't care, because they run full-out. However, > users do not run benchmarks nearly as much as they run > actual workloads... >
I think we can solve it at the guest level. The paravirt ticketlock stuff introduces wait/wake calls (actually wait is just a HLT instruction); we could spin for a while, then HLT until the other side wakes us. We should do this for all sites that busy wait.
-- error compiling committee.c: too many arguments to function
| |