Eric, I'll test the patch with the same testcase and let you all know.
Really appreciate everybody's efforts. On Wed, Jun 11, 2014 at 5:55 PM, Eric W. Biederman <ebied...@xmission.com> wrote: > "Paul E. McKenney" <paul...@linux.vnet.ibm.com> writes: > >> On Wed, Jun 11, 2014 at 01:27:07PM -0500, Dave Chiluk wrote: >>> On 06/11/2014 11:18 AM, Paul E. McKenney wrote: >>> > On Wed, Jun 11, 2014 at 10:46:00AM -0500, David Chiluk wrote: >>> >> Now think about what happens when a gateway goes down, the namespaces >>> >> need to be migrated, or a new machine needs to be brought up to replace >>> >> it. When we're talking about 3000 namespaces, the amount of time it >>> >> takes simply to recreate the namespaces becomes very significant. >>> >> >>> >> The script is a stripped down example of what exactly is being done on >>> >> the neutron gateway in order to create namespaces. >>> > >>> > Are the namespaces torn down and recreated one at a time, or is there some >>> > syscall, ioctl(), or whatever that allows bulk tear down and recreating? >>> > >>> > Thanx, Paul >>> >>> In the normal running case, the namespaces are created one at a time, as >>> new customers create a new set of VMs on the cloud. >>> >>> However, in the case of failover to a new neutron gateway the namespaces >>> are created all at once using the ip command (more or less serially). >>> >>> As far as I know there is no syscall or ioctl that allows bulk tear down >>> and recreation. if such a beast exists that might be helpful. >> >> The solution might be to create such a beast. I might be able to shave >> a bit of time off of this benchmark, but at the cost of significant >> increases in RCU's CPU consumption. A bulk teardown/recreation API could >> reduce the RCU grace-period overhead by several orders of magnitude by >> having a single RCU grace period cover a few thousand changes. >> >> This is why other bulk-change syscalls exist. >> >> Just out of curiosity, what syscalls does the ip command use? > > You can look in iproute2 ip/ipnetns.c > > But rought ip netns add does: > > unshare(CLONE_NEWNET); > mkdir /var/run/netns/<name> > mount --bind /proc/self/ns/net /var/run/netns/<name> > > I don't know if there is any sensible way to batch that work. > > (The unshare gets you into copy_net_ns in net/core/net_namespace.c > and to find all of the code it can call you have to trace all > of the register_pernet_subsys and register_pernet_device calls). > > At least for creation I would like to see if we can make all of the > rcu_callback synchronize_rcu calls go away. That seems preferable > to batching at creation time. > > Eric -- -- Rafael David Tinoco Software Sustaining Engineer @ Canonical Canonical Technical Services Engineering Team # Email: rafael.tin...@canonical.com (GPG: 87683FC0) # Phone: +55.11.9.6777.2727 (Americas/Sao_Paulo) # LP: ~inaddy | IRC: tinoco | Skype: rafael.tinoco -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/