1. 21 Oct, 2015 3 commits
    • Yuchung Cheng's avatar
      tcp: track min RTT using windowed min-filter · f6722583
      Yuchung Cheng authored
      Kathleen Nichols' algorithm for tracking the minimum RTT of a
      data stream over some measurement window. It uses constant space
      and constant time per update. Yet it almost always delivers
      the same minimum as an implementation that has to keep all
      the data in the window. The measurement window is tunable via
      sysctl.net.ipv4.tcp_min_rtt_wlen with a default value of 5 minutes.
      The algorithm keeps track of the best, 2nd best & 3rd best min
      values, maintaining an invariant that the measurement time of
      the n'th best >= n-1'th best. It also makes sure that the three
      values are widely separated in the time window since that bounds
      the worse case error when that data is monotonically increasing
      over the window.
      Upon getting a new min, we can forget everything earlier because
      it has no value - the new min is less than everything else in the
      window by definition and it's the most recent. So we restart fresh
      on every new min and overwrites the 2nd & 3rd choices. The same
      property holds for the 2nd & 3rd best.
      Therefore we have to maintain two invariants to maximize the
      information in the samples, one on values (1st.v <= 2nd.v <=
      3rd.v) and the other on times (now-win <=1st.t <= 2nd.t <= 3rd.t <=
      now). These invariants determine the structure of the code
      The RTT input to the windowed filter is the minimum RTT measured
      from ACK or SACK, or as the last resort from TCP timestamps.
      The accessor tcp_min_rtt() returns the minimum RTT seen in the
      window. ~0U indicates it is not available. The minimum is 1usec
      even if the true RTT is below that.
      Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
      Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
      Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • Yuchung Cheng's avatar
      tcp: apply Kern's check on RTTs used for congestion control · 9e45a3e3
      Yuchung Cheng authored
      Currently ca_seq_rtt_us does not use Kern's check. Fix that by
      checking if any packet acked is a retransmit, for both RTT used
      for RTT estimation and congestion control.
      Fixes: 5b08e47c
       ("tcp: prefer packet timing to TS-ECR for RTT")
      Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
      Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
      Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • David S. Miller's avatar
      Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/jkirsher/next-queue · c8fdc324
      David S. Miller authored
      Jeff Kirsher says:
      Intel Wired LAN Driver Updates 2015-10-19
      This series contains updates to i40e and i40evf only.
      Kiran adds a spinlock around code accessing VSI MAC filter list to
      ensure that we are synchronizing access to the filter list, otherwise
      we can end up with multiple accesses at the same time which can cause
      the VSI MAC filter list to get in an unstable or corrupted state.
      Jesse fixes overlong BIT defines, where the RSS enabling call were
      mistakenly missed.  Also fixes a bug where the enable function was
      enabling the interrupt twice while trying to update the two interrupt
      throttle rate thresholds for Rx and Tx, while refactoring the IRQ
      enable function to simplify reading the flow.  Addressed the high
      CPU utilization of some small streaming workloads that the driver should
      reduce CPU in.
      Anjali fixes two X722 issues with respect to EEPROM checksum verify and
      reading NVM version info.  Fixed where a mask value was accidentally
      replaced with a bit mask causing Flow Director sideband to be broken.
      Alex Duyck fixes areas of the drivers which run from hard interrupt
      context or with interrupts already disabled in netpoll, so use
      napi_schedule_irqoff() instead of napi_schedule().
      Mitch fixes the VF drivers to not easily give up when it is not able
      to communicate with the PF driver.
      Carolyn fixes a problem where our tools MAC loopback test, after driver
      unbind would fail because the hardware was configured for multiqueue and
      unbind operation did not clear this configuration.  Also fixed a issue
      where the NVMUpdate tool gets bad data from the PHY when using the PHY
      NVM feature because of contention on the MDIO interface from getting
      PHY capability calls from the driver during regular operations.
      Catherine fixed an issue where we were checking if autoneg was allowed
      to change before checking if autoneg was changing, these checks need to
      be in the reverse order.
      Jean Sacren fixes up an function header comment to align the kernel-docs
      with the actual code.
      v2: Cleaned up the use of spin_is_locked() in patch 1 based on feedback
          from David Miller, since it always evaluates to zero on uni-processor
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
  2. 20 Oct, 2015 1 commit
  3. 19 Oct, 2015 36 commits