diff mbox series

[net,v4,3/3] tcp_cubic: fix to use emulated Reno cwnd one RTT in the future

Message ID 20240817163400.2616134-4-mrzhang97@gmail.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series tcp_cubic: fix to achieve at least the same throughput as Reno | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 16 this patch: 16
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers fail 1 blamed authors not CCed: stephen@networkplumber.org; 4 maintainers not CCed: pabeni@redhat.com kuba@kernel.org stephen@networkplumber.org dsahern@kernel.org
netdev/build_clang success Errors and warnings before: 16 this patch: 16
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 16 this patch: 16
netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-08-17--18-00 (tests: 709)

Commit Message

Mingrui Zhang Aug. 17, 2024, 4:34 p.m. UTC 
The original code estimates RENO snd_cwnd using the estimated 
RENO snd_cwnd at the current time (i.e., tcp_cwnd).

The patched code estimates RENO snd_cwnd using the estimated 
RENO snd_cwnd after one RTT (i.e., tcp_cwnd_next_rtt), 
because ca->cnt is used to increase snd_cwnd for the next RTT.

Fixes: 89b3d9aaf467 ("[TCP] cubic: precompute constants")
Signed-off-by: Mingrui Zhang <mrzhang97@gmail.com>
Signed-off-by: Lisong Xu <xu@unl.edu>
---
v3->v4: Separate declarations and code of tcp_cwnd_next_rtt
v2->v3: Correct the "Fixes:" footer content
v1->v2: Separate patches

 net/ipv4/tcp_cubic.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 03cfbad37dab..2d7121ca789e 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -304,7 +304,7 @@  static inline void bictcp_update(struct bictcp *ca, u32 cwnd, u32 acked)
 tcp_friendliness:
 	/* TCP Friendly */
 	if (tcp_friendliness) {
-		u32 scale = beta_scale;
+		u32 scale = beta_scale, tcp_cwnd_next_rtt;
 
 		if (cwnd < ca->cwnd_prior)
 			delta = (cwnd * scale) >> 3;	/* CUBIC additive increment */
@@ -315,8 +315,11 @@  static inline void bictcp_update(struct bictcp *ca, u32 cwnd, u32 acked)
 			ca->tcp_cwnd++;
 		}
 
-		if (ca->tcp_cwnd > cwnd) {	/* if bic is slower than tcp */
-			delta = ca->tcp_cwnd - cwnd;
+		/* Reno cwnd one RTT in the future */
+		tcp_cwnd_next_rtt = ca->tcp_cwnd + (ca->ack_cnt + cwnd) / delta;
+
+		if (tcp_cwnd_next_rtt > cwnd) {  /* if bic is slower than Reno */
+			delta = tcp_cwnd_next_rtt - cwnd;
 			max_cnt = cwnd / delta;
 			if (ca->cnt > max_cnt)
 				ca->cnt = max_cnt;