On Tue, Jul 7, 2015 at 9:17 AM, David Ahern <dsahern@xxxxxxxxx> wrote: > On 7/7/15 9:56 AM, Andy Lutomirski wrote: >> >> Netlink is fine for these use cases (if they were related to the >> netns, not the pid ns or user ns), and it works. It's still tedious >> -- I bet that if you used a syscall, the user code would be >> considerable shorter, though. :) >> >> How would this be a problem if you used plain syscalls? The user >> would make a request, and the syscall would tell the user that their >> result buffer was too small if it was, in fact, too small. > > > It will be impossible to tell a user what sized buffer is needed. The size > is largely a function of the number of tasks and number of maps per thread > group and both of those will be changing. With the growing size of systems > (I was sparc systems with 1024 cpus) the workload can be 10's of thousands > of tasks each with a lot of maps (e.g., java workloads). That amounts to a > non-trivial amount of data that has to be pushed to userspace. > > One of the benefits of the netlink approach is breaking the data across > multiple messages and picking up where you left off. That infrastructure is > already in place. > How does picking up where you left off work? I assumed the interface was something along the lines of "give me information starting from pid N", but maybe I missed something. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
