On 29/04/18 08:31 PM, David Miller wrote:
Well, two things:
1) The congestion control info is opt-in, meaning that the user gets
it in the dump if they ask for it.
This information is opt-in, because otherwise the dumps get really
large.
Therefore, emitting this stuff by default on destroys in a
non-starter.
There are two options that I investigated:
Add a setsockopt() for a new group that indicate "give me the congestion
info in addition" or add a similar knob at bind() time. Either of those
approaches would require bigger surgeries. If you think either of those
is reasonable i will work in that direction.
Note: Vegas adds 4 32-bit words; BBR 5 32-bit words; the congestion
name another 16B worst case.
In the larger scope of things that is very small extra data and saves
all the complexity of the other approaches.
2) The TCP_TIME_WAIT test is not there for looks. You need to add it
also to the destroy case, and guess what? All the sockets you will
see will not pass that test.
The TCP_TIME_WAIT test makes sense for a live socket. This sock is
past that stage.
I'm not applying this, sorry. I really think things are go as-is, and
if you really truly want the congestion control information you can
ask for it while the socket is still alive, and is in the proper state
to sample the congestion control state before you kill it off.
I am avoiding the polling for scaling reasons. It worked fine for
small number of sockets.
cheers,
jamal
