On 16/09/2015 14:22, Oleg Nesterov wrote: > > The issue is that rcu_sync doesn't eliminate synchronize_sched, > > Yes, but it eliminates _expedited(). This is good, but otoh this means > that (say) individual __cgroup_procs_write() can take much more time. > However, it won't block the readers and/or disturb the whole system. According to Christian, removing the _expedited() "makes things worse" in that the system takes ages to boot up and systemd timeouts. So I'm still a bit wary about anything that uses RCU for the cgroups write side. However, rcu_sync is okay with him, so perhaps it is really really effective. Christian, can you instrument how many synchronize_sched (out of the 6479 cgroup_procs_write calls) are actually executed at boot with the rcu rework? Paolo > And percpu_up_write() doesn't do synchronize_sched() at all. -- 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
