On Fri, 30 Jun 2006 23:37:10 -0400 Shailabh Nagar <[EMAIL PROTECTED]> wrote:
> >Set aside the implementation details and ask "what is a good design"? > > > >A kernel-wide constant, whether determined at build-time or by a /proc poke > >isn't a nice design. > > > >Can we permit userspace to send in a netlink message describing a cpumask? > >That's back-compatible. > > > > > Yes, that should be doable. And passing in a cpumask is much better > since we no longer > have to maintain mappings. > > So the strawman is: > Listener bind()s to genetlink using its real pid. > Sends a separate "registration" message with cpumask to listen to. > Kernel stores (real) pid and cpumask. > During task exit, kernel goes through each registered listener (small > list) and decides which > one needs to get this exit data and calls a genetlink_unicast to each > one that does need it. > > If number of listeners is small, the lookups should be swift enough. If > it grows large, we > can consider a fancier lookup (but there I go again, delving into > implementation too early :-) We'll need a map. 1024 CPUs, 1024 listeners, 1000 exits/sec/CPU and we're up to a million operations per second per CPU. Meltdown. But it's a pretty simple map. A per-cpu array of pointers to the head of a linked list. One lock for each CPU's list. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
