On Thu, Oct 22, 2015 at 12:21:31AM -0400, Johannes Weiner wrote:

The tcp memory controller has extensive provisions for future memory
accounting interfaces that won't materialize after all. Cut the code
base down to what's actually used, now and in the likely future.

- There won't be any different protocol counters in the future, so a
  direct sock->sk_memcg linkage is enough. This eliminates a lot of
  callback maze and boilerplate code, and restores most of the socket
  allocation code to pre-tcp_memcontrol state.

- There won't be a tcp control soft limit, so integrating the memcg

In fact, the code is ready for the "soft" limit (I mean min, pressure,
max tuple), it just lacks a knob.

  code into the global skmem limiting scheme complicates things
  unnecessarily. Replace all that with simple and clear charge and
  uncharge calls--hidden behind a jump label--to account skb memory.

- The previous jump label code was an elaborate state machine that
  tracked the number of cgroups with an active socket limit in order
  to enable the skmem tracking and accounting code only when actively
  necessary. But this is overengineered: it was meant to protect the
  people who never use this feature in the first place. Simply enable
  the branches once when the first limit is set until the next reboot.

...

AFAIU, now we won't shrink the window on hitting the limit, i.e. this
patch subtly changes the behavior of the existing knobs, potentially
breaking them.

Thanks,
Vladimir

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