From: Eric Dumazet <eduma...@google.com> Date: Tue, 25 Apr 2017 10:15:31 -0700
> Some devices or linux distributions use HZ=100 or HZ=250 > > TCP receive buffer autotuning has poor behavior caused by this choice. > Since autotuning happens after 4 ms or 10 ms, short distance flows > get their receive buffer tuned to a very high value, but after an initial > period where it was frozen to (too small) initial value. > > With BBR (or other CC allowing to increase BDP), we are willing to > increase tcp_rmem[2], but this receive autotuning defect is a blocker > for hosts dealing with gazillions of TCP flows in the data centers, > since many of them have inflated RCVBUF. Risk of OOM is too high. > > Note that TSO autodefer, tcp cubic, and TCP TS options (RFC 7323) > also suffer from our dependency to jiffies (via tcp_time_stamp). > > We have ongoing efforts to improve all that in the future. Looks great, series applied, thanks Eric.
