Author: smh
Date: Mon Apr 10 08:19:35 2017
New Revision: 316676
URL: https://svnweb.freebsd.org/changeset/base/316676
Log:
Use estimated RTT for receive buffer auto resizing instead of
timestamps
Switched from using timestamps to RTT estimates when performing
TCP receive
buffer auto resizing, as not all hosts support / enable TCP
timestamps.
Disabled reset of receive buffer auto scaling when not in bulk
receive mode,
which gives an extra 20% performance increase.
Also extracted auto resizing to a common method shared between
standard and
fastpath modules.
With this AWS S3 downloads at ~17ms latency on a 1Gbps
connection jump from
~3MB/s to ~100MB/s using the default settings.
Reviewed by: lstewart, gnn
MFC after: 2 weeks
Relnotes: Yes
Sponsored by: Multiplay
Differential Revision: https://reviews.freebsd.org/D9668
Modified:
head/sys/netinet/in_kdtrace.c
head/sys/netinet/in_kdtrace.h
head/sys/netinet/tcp_input.c
head/sys/netinet/tcp_output.c
head/sys/netinet/tcp_stacks/fastpath.c
head/sys/netinet/tcp_var.h
Modified: head/sys/netinet/in_kdtrace.c
==============================================================================
--- head/sys/netinet/in_kdtrace.c Mon Apr 10 06:19:09 2017 (r316675)
+++ head/sys/netinet/in_kdtrace.c Mon Apr 10 08:19:35 2017 (r316676)
@@ -132,6 +132,14 @@ SDT_PROBE_DEFINE6_XLATE(tcp, , , state__
"void *", "void *",
"int", "tcplsinfo_t *");
+SDT_PROBE_DEFINE6_XLATE(tcp, , , receive__autoresize,
+ "void *", "void *",
+ "struct tcpcb *", "csinfo_t *",
+ "struct mbuf *", "ipinfo_t *",
+ "struct tcpcb *", "tcpsinfo_t *" ,
+ "struct tcphdr *", "tcpinfoh_t *",
+ "int", "int");
+
SDT_PROBE_DEFINE5_XLATE(udp, , , receive,
"void *", "pktinfo_t *",
"struct inpcb *", "csinfo_t *",
Modified: head/sys/netinet/in_kdtrace.h
==============================================================================
--- head/sys/netinet/in_kdtrace.h Mon Apr 10 06:19:09 2017 (r316675)
+++ head/sys/netinet/in_kdtrace.h Mon Apr 10 08:19:35 2017 (r316676)
@@ -65,6 +65,7 @@ SDT_PROBE_DECLARE(tcp, , , debug__input)
SDT_PROBE_DECLARE(tcp, , , debug__output);
SDT_PROBE_DECLARE(tcp, , , debug__user);
SDT_PROBE_DECLARE(tcp, , , debug__drop);
+SDT_PROBE_DECLARE(tcp, , , receive__autoresize);
SDT_PROBE_DECLARE(udp, , , receive);
SDT_PROBE_DECLARE(udp, , , send);
Modified: head/sys/netinet/tcp_input.c
==============================================================================
--- head/sys/netinet/tcp_input.c Mon Apr 10 06:19:09 2017 (r316675)
+++ head/sys/netinet/tcp_input.c Mon Apr 10 08:19:35 2017 (r316676)
@@ -1486,6 +1486,68 @@ drop:
return (IPPROTO_DONE);
}
+/*
+ * Automatic sizing of receive socket buffer. Often the send
+ * buffer size is not optimally adjusted to the actual network
+ * conditions at hand (delay bandwidth product). Setting the
+ * buffer size too small limits throughput on links with high
+ * bandwidth and high delay (eg. trans-continental/oceanic links).
+ *
+ * On the receive side the socket buffer memory is only rarely
+ * used to any significant extent. This allows us to be much
+ * more aggressive in scaling the receive socket buffer. For
+ * the case that the buffer space is actually used to a large
+ * extent and we run out of kernel memory we can simply drop
+ * the new segments; TCP on the sender will just retransmit it
+ * later. Setting the buffer size too big may only consume too
+ * much kernel memory if the application doesn't read() from
+ * the socket or packet loss or reordering makes use of the
+ * reassembly queue.
+ *
+ * The criteria to step up the receive buffer one notch are:
+ * 1. Application has not set receive buffer size with
+ * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
+ * 2. the number of bytes received during the time it takes
+ * one timestamp to be reflected back to us (the RTT);
+ * 3. received bytes per RTT is within seven eighth of the
+ * current socket buffer size;
+ * 4. receive buffer size has not hit maximal automatic size;
+ *
+ * This algorithm does one step per RTT at most and only if
+ * we receive a bulk stream w/o packet losses or reorderings.
+ * Shrinking the buffer during idle times is not necessary as
+ * it doesn't consume any memory when idle.
+ *
+ * TODO: Only step up if the application is actually serving
+ * the buffer to better manage the socket buffer resources.
+ */
+int
+tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so,
+ struct tcpcb *tp, int tlen)
+{
+ int newsize = 0;
+
+ if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) &&
+ tp->t_srtt != 0 && tp->rfbuf_ts != 0 &&
+ TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) >
+ (tp->t_srtt >> TCP_RTT_SHIFT)) {
+ if (tp->rfbuf_cnt > (so->so_rcv.sb_hiwat / 8 * 7) &&
+ so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) {
+ newsize = min(so->so_rcv.sb_hiwat +
+ V_tcp_autorcvbuf_inc, V_tcp_autorcvbuf_max);
+ }
+ TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize);
+
+ /* Start over with next RTT. */
+ tp->rfbuf_ts = 0;
+ tp->rfbuf_cnt = 0;
+ } else {
+ tp->rfbuf_cnt += tlen; /* add up */
+ }
+
+ return (newsize);
+}
+
void
tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
@@ -1849,62 +1911,7 @@ tcp_do_segment(struct mbuf *m, struct tc
#endif
TCP_PROBE3(debug__input, tp, th, m);
- /*
- * Automatic sizing of receive socket buffer. Often the send
- * buffer size is not optimally adjusted to the actual network
- * conditions at hand (delay bandwidth product). Setting the
- * buffer size too small limits throughput on links with high
- * bandwidth and high delay (eg. trans-continental/oceanic
links).
- *
- * On the receive side the socket buffer memory is only rarely
- * used to any significant extent. This allows us to be much
- * more aggressive in scaling the receive socket buffer. For
- * the case that the buffer space is actually used to a large
- * extent and we run out of kernel memory we can simply drop
- * the new segments; TCP on the sender will just retransmit it
- * later. Setting the buffer size too big may only consume too
- * much kernel memory if the application doesn't read() from
- * the socket or packet loss or reordering makes use of the
- * reassembly queue.
- *
- * The criteria to step up the receive buffer one notch are:
- * 1. Application has not set receive buffer size with
- * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
- * 2. the number of bytes received during the time it takes
- * one timestamp to be reflected back to us (the RTT);
- * 3. received bytes per RTT is within seven eighth of the
- * current socket buffer size;
- * 4. receive buffer size has not hit maximal automatic size;
- *
- * This algorithm does one step per RTT at most and only if
- * we receive a bulk stream w/o packet losses or reorderings.
- * Shrinking the buffer during idle times is not necessary as
- * it doesn't consume any memory when idle.
- *
- * TODO: Only step up if the application is actually serving
- * the buffer to better manage the socket buffer resources.
- */
- if (V_tcp_do_autorcvbuf &&
- (to.to_flags & TOF_TS) &&
- to.to_tsecr &&
- (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
- if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) &&
- to.to_tsecr - tp->rfbuf_ts < hz) {
- if (tp->rfbuf_cnt >
- (so->so_rcv.sb_hiwat / 8 * 7) &&
- so->so_rcv.sb_hiwat <
- V_tcp_autorcvbuf_max) {
- newsize =
- min(so->so_rcv.sb_hiwat +
- V_tcp_autorcvbuf_inc,
- V_tcp_autorcvbuf_max);
- }
- /* Start over with next RTT. */
- tp->rfbuf_ts = 0;
- tp->rfbuf_cnt = 0;
- } else
- tp->rfbuf_cnt += tlen; /* add up */
- }
+ newsize = tcp_autorcvbuf(m, th, so, tp, tlen);
/* Add data to socket buffer. */
SOCKBUF_LOCK(&so->so_rcv);
@@ -1945,10 +1952,6 @@ tcp_do_segment(struct mbuf *m, struct tc
win = 0;
tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
- /* Reset receive buffer auto scaling when not in bulk receive
mode. */
- tp->rfbuf_ts = 0;
- tp->rfbuf_cnt = 0;
-
switch (tp->t_state) {
/*
Modified: head/sys/netinet/tcp_output.c
==============================================================================
--- head/sys/netinet/tcp_output.c Mon Apr 10 06:19:09 2017 (r316675)
+++ head/sys/netinet/tcp_output.c Mon Apr 10 08:19:35 2017 (r316676)
@@ -831,11 +831,13 @@ send:
to.to_tsval = tcp_ts_getticks() + tp->ts_offset;
to.to_tsecr = tp->ts_recent;
to.to_flags |= TOF_TS;
- /* Set receive buffer autosizing timestamp. */
- if (tp->rfbuf_ts == 0 &&
- (so->so_rcv.sb_flags & SB_AUTOSIZE))
- tp->rfbuf_ts = tcp_ts_getticks();
}
+
+ /* Set receive buffer autosizing timestamp. */
+ if (tp->rfbuf_ts == 0 &&
+ (so->so_rcv.sb_flags & SB_AUTOSIZE))
+ tp->rfbuf_ts = tcp_ts_getticks();
+
/* Selective ACK's. */
if (tp->t_flags & TF_SACK_PERMIT) {
if (flags & TH_SYN)
Modified: head/sys/netinet/tcp_stacks/fastpath.c
==============================================================================
--- head/sys/netinet/tcp_stacks/fastpath.c Mon Apr 10 06:19:09
2017 (r316675)
+++ head/sys/netinet/tcp_stacks/fastpath.c Mon Apr 10 08:19:35
2017 (r316676)
@@ -399,62 +399,8 @@ tcp_do_fastnewdata(struct mbuf *m, struc
(void *)tcp_saveipgen, &tcp_savetcp, 0);
#endif
TCP_PROBE3(debug__input, tp, th, m);
- /*
- * Automatic sizing of receive socket buffer. Often the send
- * buffer size is not optimally adjusted to the actual network
- * conditions at hand (delay bandwidth product). Setting the
- * buffer size too small limits throughput on links with high
- * bandwidth and high delay (eg. trans-continental/oceanic links).
- *
- * On the receive side the socket buffer memory is only rarely
- * used to any significant extent. This allows us to be much
- * more aggressive in scaling the receive socket buffer. For
- * the case that the buffer space is actually used to a large
- * extent and we run out of kernel memory we can simply drop
- * the new segments; TCP on the sender will just retransmit it
- * later. Setting the buffer size too big may only consume too
- * much kernel memory if the application doesn't read() from
- * the socket or packet loss or reordering makes use of the
- * reassembly queue.
- *
- * The criteria to step up the receive buffer one notch are:
- * 1. Application has not set receive buffer size with
- * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
- * 2. the number of bytes received during the time it takes
- * one timestamp to be reflected back to us (the RTT);
- * 3. received bytes per RTT is within seven eighth of the
- * current socket buffer size;
- * 4. receive buffer size has not hit maximal automatic size;
- *
- * This algorithm does one step per RTT at most and only if
- * we receive a bulk stream w/o packet losses or reorderings.
- * Shrinking the buffer during idle times is not necessary as
- * it doesn't consume any memory when idle.
- *
- * TODO: Only step up if the application is actually serving
- * the buffer to better manage the socket buffer resources.
- */
- if (V_tcp_do_autorcvbuf &&
- (to->to_flags & TOF_TS) &&
- to->to_tsecr &&
- (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
- if (TSTMP_GT(to->to_tsecr, tp->rfbuf_ts) &&
- to->to_tsecr - tp->rfbuf_ts < hz) {
- if (tp->rfbuf_cnt >
- (so->so_rcv.sb_hiwat / 8 * 7) &&
- so->so_rcv.sb_hiwat <
- V_tcp_autorcvbuf_max) {
- newsize =
- min(so->so_rcv.sb_hiwat +
- V_tcp_autorcvbuf_inc,
- V_tcp_autorcvbuf_max);
- }
- /* Start over with next RTT. */
- tp->rfbuf_ts = 0;
- tp->rfbuf_cnt = 0;
- } else
- tp->rfbuf_cnt += tlen; /* add up */
- }
+
+ newsize = tcp_autorcvbuf(m, th, so, tp, tlen);
/* Add data to socket buffer. */
SOCKBUF_LOCK(&so->so_rcv);
@@ -532,10 +478,6 @@ tcp_do_slowpath(struct mbuf *m, struct t
win = 0;
tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
- /* Reset receive buffer auto scaling when not in bulk receive
mode. */
- tp->rfbuf_ts = 0;
- tp->rfbuf_cnt = 0;
-
switch (tp->t_state) {
/*
Modified: head/sys/netinet/tcp_var.h
==============================================================================
--- head/sys/netinet/tcp_var.h Mon Apr 10 06:19:09 2017 (r316675)
+++ head/sys/netinet/tcp_var.h Mon Apr 10 08:19:35 2017 (r316676)
@@ -778,6 +778,8 @@ void hhook_run_tcp_est_in(struct tcpcb *
#endif
int tcp_input(struct mbuf **, int *, int);
+int tcp_autorcvbuf(struct mbuf *, struct tcphdr *, struct socket *,
+ struct tcpcb *, int);
void tcp_do_segment(struct mbuf *, struct tcphdr *,
struct socket *, struct tcpcb *, int, int, uint8_t,
int);
