From 783d3adfdb0a074ae7a6e0dd37fe8efaf7e2b39a Mon Sep 17 00:00:00 2001 From: Dimitri Staessens Date: Sun, 3 Apr 2022 12:01:20 +0200 Subject: lib: Fix RTO update on timeout This fixes the RTO doubling on timeout according to Karn/Partridge. Exponentially increasing RTO when it times out (e.g. doubling) fixes the problem that a sudden increase in real RTT starves the sRTT updates by never getting out of backoff as retransmitted packets can't update RTT. Added an parameter to make it less aggressive, default is doubling. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders --- src/lib/timerwheel.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) (limited to 'src/lib/timerwheel.c') diff --git a/src/lib/timerwheel.c b/src/lib/timerwheel.c index f30f867d..cf4e1eef 100644 --- a/src/lib/timerwheel.c +++ b/src/lib/timerwheel.c @@ -36,7 +36,6 @@ struct rxm { struct frct_pci * pkt; size_t len; time_t t0; /* Time when original was sent (us). */ - size_t mul; /* RTO multiplier. */ struct frcti * frcti; int fd; int flow_id; /* Prevent rtx when fd reused. */ @@ -166,9 +165,7 @@ static void timerwheel_move(void) struct flow * f; uint32_t snd_lwe; uint32_t rcv_lwe; - time_t rto; size_t lvl = 0; - time_t act; r = list_entry(p, struct rxm, next); @@ -188,8 +185,6 @@ static void timerwheel_move(void) snd_lwe = snd_cr->lwe; rcv_lwe = rcv_cr->lwe; - rto = r->frcti->rto; - act = ts_to_ns(r->frcti->rcv_cr.act); pthread_rwlock_unlock(&r->frcti->lock); @@ -203,20 +198,20 @@ static void timerwheel_move(void) pthread_rwlock_wrlock(&r->frcti->lock); - if (r->frcti->probe - && (r->frcti->rttseq == r->seqno)) + if (r->seqno == r->frcti->rttseq) { + r->frcti->rto += + f->frcti->rto >> RTO_DIV; r->frcti->probe = false; + } #ifdef PROC_FLOW_STATS r->frcti->n_rtx++; #endif - pthread_rwlock_unlock(&r->frcti->lock); + rslot = r->frcti->rto >> RXMQ_RES; - if (ts_to_ns(now) - act > (rto << 2)) - rto <<= r->mul++; + pthread_rwlock_unlock(&r->frcti->lock); /* Schedule at least in the next time slot. */ slot = ts_to_ns(now) >> RXMQ_RES; - rslot = rto >> RXMQ_RES; while (rslot >= RXMQ_SLOTS) { ++lvl; @@ -326,7 +321,6 @@ static int timerwheel_rxm(struct frcti * frcti, clock_gettime(PTHREAD_COND_CLOCK, &now); r->t0 = ts_to_ns(now); - r->mul = 0; r->seqno = seqno; r->frcti = frcti; r->len = shm_du_buff_len(sdb); -- cgit v1.2.3