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ea94549cb2
This makes a couple of simple re-arrangements in lwip_selscan() that
should improve performance in the following ways:
1) The old code linearly walked all sockets to maxfd regardless of
whether they were set in the fd set. The process involved
acquiring sys arch protect, looking up the socket, and then
checking if the socket was present in any of the fd sets. On
systems with lots of sockets and a heavy SYS_ARCH_PROTECT
infrastructure (a mutex) this can result in a lot of extra work.
Now we skip this process for any fd that is not in the input sets
2) If the socket from tryget_socket() is NULL we no longer continue
and compare the input fd sets with a zeroed out set of events
3) We no longer need to zero out our event sets because they are
only accessed when tryget_socket() is successful
lwip_selscan() is called at most once per select call and sometimes up to three times