Am 16.09.2015 um 13:03 schrieb Tejun Heo: > Hello, > > On Wed, Sep 16, 2015 at 12:58:00PM +0200, Christian Borntraeger wrote: >> FWIW, I added a printk to percpu_down_write. With KVM and uprobes disabled, >> just booting up a fedora20 gives me __6749__ percpu_down_write calls on 4.2. >> systemd seems to do that for the processes. >> >> So a revert is really the right thing to do. In fact, I dont know if the >> rcu_sync_enter rework is enough. With systemd setting the cgroup seem to >> be NOT a cold/seldom case. > > Booting would usually be the hottest operation for that and it's still > *relatively* cold path compared to the reader side which is task > fork/exit paths. The whole point is shift overhead from hotter reader > side. Can you see problems with percpu_rwsem rework? As I said, it seems the rcu tree with that change seems to work fine on my system. This needs a more testing on other machines, though. I guess a revert plus a re-add in the 4.4 merge window should give us enough test coverage. Christian -- 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
