On Fri, 30 Jun 2006 22:20:23 -0400Yes, that should be doable. And passing in a cpumask is much better since we no longer
Shailabh Nagar <nagar@xxxxxxxxxxxxxx> wrote:
If we're going to abuse nl_pid then how about we design things so thatAll these options mean each listener gets to pick a "custom" range of cpus to listen on, rather than choose one of pre-defined ranges (even if the pre-defined ranges can change
nl_pid is treated as two 16-bit words - one word is the start CPU and the
other word is the end cpu?
Or, if a 65536-CPU limit is too scary, make the bottom 8 bits of nl_pid be
the number of CPUS (ie: TASKSTATS_CPUS_PER_SET) and the top 24 bits is the
starting CPU.
<avoids mentioning nl_pad>
It'd be better to use a cpumask, of course..
by a configurable TASKSTATS_CPUS_PER_SET). Which means the kernel side has to
figure out which of the listeners cpu range includes the currently exiting task's cpu. To do
this, we'll need a callback from the binding of the netlink socket (so taskstats can maintain
the cpu -> nl_pid mappings at any exit).
The current genetlink interface doesn't have that kind of flexibility (though it can be added
I'm sure).
Seems a bit involved if the primary aim is to restrict the number of cpus that one listener
wants to listen, rather than be able to pick which ones.
A configurable range won't suffice ?
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.