On Thu, Jul 27, 2017 at 4:31 PM, Florian Westphal <f...@strlen.de> wrote: > > This RFC removes tcp prequeueing and header prediction support. > > After a hallway discussion with Eric Dumazet some > maybe-not-so-useful-anymore TCP stack features came up, HP and > Prequeue among these. > > So this RFC proposes to axe both. > > In brief, TCP prequeue assumes a single-process-blocking-read > design, which is not that common anymore, and the most frequently > used high-performance networking program that does this is netperf :) > > With more commong (e)poll designs, prequeue doesn't work. > > The idea behind prequeueing isn't so bad in itself; it moves > part of tcp processing -- including ack processing (including > retransmit queue processing) into process context. > However, removing it would not just avoid some code, for most > programs it elimiates dead code. > > As processing then always occurs in BH context, it would allow us > to experiment e.g. with bulk-freeing of skb heads when a packet acks > data on the retransmit queue. > > Header prediction is also less useful nowadays. > For packet trains, GRO will aggregate packets so we do not get > a per-packet benefit. > Header prediction will also break down with light packet loss due to SACK. > > So, In short: What do others think? +2 for this move. Will review the patches soon.
> > Florian Westphal (6): > tcp: remove prequeue support > tcp: reindent two spots after prequeue removal > tcp: remove low_latency sysctl > tcp: remove header prediction > tcp: remove CA_ACK_SLOWPATH > tcp: remove unused mib counters > > Documentation/networking/ip-sysctl.txt | 7 > include/linux/tcp.h | 15 - > include/net/tcp.h | 40 ---- > include/uapi/linux/snmp.h | 8 > net/ipv4/proc.c | 8 > net/ipv4/sysctl_net_ipv4.c | 3 > net/ipv4/tcp.c | 109 ----------- > net/ipv4/tcp_input.c | 303 > +++------------------------------ > net/ipv4/tcp_ipv4.c | 63 ------ > net/ipv4/tcp_minisocks.c | 3 > net/ipv4/tcp_output.c | 2 > net/ipv4/tcp_timer.c | 12 - > net/ipv4/tcp_westwood.c | 31 --- > net/ipv6/tcp_ipv6.c | 3 > 14 files changed, 43 insertions(+), 564 deletions(-) >
