diff options
| author | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-03-07 14:42:35 +0000 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-03-07 14:42:35 +0000 |
| commit | 3ba4cea21901d90d703b52e4a806fbafa86037a6 (patch) | |
| tree | b556d880492a783861a39c8197e35d56ac4c77f9 /net/ipv4/tcp_input.c | |
| parent | a2e6177c931793b4ffb30e722fce6fc7aaff9fa5 (diff) | |
| parent | 8e781f65423c2e8e65a56972ba996b6c01a5ef3e (diff) | |
Merge branch 'for-rmk/perf' of git://git.kernel.org/pub/scm/linux/kernel/git/will/linux into devel-stable
* Support for Qualcomm Krait processors (run perf on your phone!)
* Support for Cortex-A12 (run perf stat on your FPGA!)
* Support for perf_sample_event_took, allowing us to automatically decrease
the sample rate if we can't handle the PMU interrupts quickly enough
(run perf record on your FPGA!).
As part of the Krait support, we also gain support for PPI generation by
the PMU.
Diffstat (limited to 'net/ipv4/tcp_input.c')
| -rw-r--r-- | net/ipv4/tcp_input.c | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 65cf90e063d5..227cba79fa6b 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -671,6 +671,7 @@ static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) { struct tcp_sock *tp = tcp_sk(sk); long m = mrtt; /* RTT */ + u32 srtt = tp->srtt; /* The following amusing code comes from Jacobson's * article in SIGCOMM '88. Note that rtt and mdev @@ -688,11 +689,9 @@ static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) * does not matter how to _calculate_ it. Seems, it was trap * that VJ failed to avoid. 8) */ - if (m == 0) - m = 1; - if (tp->srtt != 0) { - m -= (tp->srtt >> 3); /* m is now error in rtt est */ - tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ + if (srtt != 0) { + m -= (srtt >> 3); /* m is now error in rtt est */ + srtt += m; /* rtt = 7/8 rtt + 1/8 new */ if (m < 0) { m = -m; /* m is now abs(error) */ m -= (tp->mdev >> 2); /* similar update on mdev */ @@ -723,11 +722,12 @@ static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) } } else { /* no previous measure. */ - tp->srtt = m << 3; /* take the measured time to be rtt */ + srtt = m << 3; /* take the measured time to be rtt */ tp->mdev = m << 1; /* make sure rto = 3*rtt */ tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); tp->rtt_seq = tp->snd_nxt; } + tp->srtt = max(1U, srtt); } /* Set the sk_pacing_rate to allow proper sizing of TSO packets. @@ -746,8 +746,10 @@ static void tcp_update_pacing_rate(struct sock *sk) rate *= max(tp->snd_cwnd, tp->packets_out); - /* Correction for small srtt : minimum srtt being 8 (1 jiffy << 3), - * be conservative and assume srtt = 1 (125 us instead of 1.25 ms) + /* Correction for small srtt and scheduling constraints. + * For small rtt, consider noise is too high, and use + * the minimal value (srtt = 1 -> 125 us for HZ=1000) + * * We probably need usec resolution in the future. * Note: This also takes care of possible srtt=0 case, * when tcp_rtt_estimator() was not yet called. |