"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 -- 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/
