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polish uTP slow start

This commit is contained in:
Arvid Norberg 2012-06-21 16:41:05 +00:00
parent 2b9b2a188a
commit 351e34f9d1
1 changed files with 18 additions and 4 deletions
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22
src/utp_stream.cpp
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@ -257,8 +257,7 @@ struct utp_socket_impl
, m_eof(false)
, m_attached(true)
, m_nagle(true)
// TODO: make slow start work
, m_slow_start(false)
, m_slow_start(true)
, m_cwnd_full(false)
, m_deferred_ack(false)
{
@ -592,7 +591,11 @@ struct utp_socket_impl
bool m_nagle:1;
// this is true while the socket is in slow start mode. It's
// only in slow-start during the start-up phase
// only in slow-start during the start-up phase. Slow start
// (contrary to what its name suggest) means that we're growing
// the congestion window (cwnd) exponetially rather than linearly.
// this is done at startup of a socket in order to find its
// link capacity faster. This behaves similar to TCP slow start
bool m_slow_start:1;
// this is true as long as we have as many packets in
@ -2784,7 +2787,7 @@ void utp_socket_impl::do_ledbat(int acked_bytes, int delay, int in_flight, ptime
boost::int64_t delay_factor = (boost::int64_t(target_delay - delay) << 16) / target_delay;
boost::int64_t scaled_gain;
if (delay >= target_delay / 2)
if (delay >= target_delay)
{
UTP_LOGV("%8p: off_target: %d slow_start -> 0\n", this, target_delay - delay);
m_slow_start = false;
@ -2802,6 +2805,10 @@ void utp_socket_impl::do_ledbat(int acked_bytes, int delay, int in_flight, ptime
scaled_gain = linear_gain;
}
// make sure we don't wrap the cwnd
if (scaled_gain >= INT64_MAX - m_cwnd)
scaled_gain = INT64_MAX - m_cwnd - 1;
if (scaled_gain > 0 && !m_cwnd_full
&& m_last_cwnd_hit + milliseconds((std::max)(m_rtt.mean(), 500)) < now)
{
@ -2811,6 +2818,7 @@ void utp_socket_impl::do_ledbat(int acked_bytes, int delay, int in_flight, ptime
// this probably means we have a send rate limit, so we shouldn't make
// the cwnd size any larger
scaled_gain = 0;
m_slow_start = false;
}
UTP_LOGV("%8p: do_ledbat delay:%d off_target: %d window_factor:%f target_factor:%f "
@ -2831,6 +2839,7 @@ void utp_socket_impl::do_ledbat(int acked_bytes, int delay, int in_flight, ptime
TORRENT_ASSERT(m_cwnd > 0);
}
TORRENT_ASSERT(m_cwnd >= 0);
int window_size_left = (std::min)(int(m_cwnd >> 16), int(m_adv_wnd)) - in_flight + acked_bytes;
if (window_size_left >= m_mtu)
@ -2839,6 +2848,9 @@ void utp_socket_impl::do_ledbat(int acked_bytes, int delay, int in_flight, ptime
, this, m_mtu, in_flight, int(m_adv_wnd), int(m_cwnd >> 16), acked_bytes);
m_cwnd_full = false;
}
if ((m_cwnd >> 16) >= m_adv_wnd)
m_slow_start = false;
}
void utp_stream::bind(endpoint_type const& ep, error_code& ec) { }
@ -2906,6 +2918,8 @@ void utp_socket_impl::tick(ptime const& now)
m_cwnd = boost::int64_t(m_mtu) << 16;
}
TORRENT_ASSERT(m_cwnd >= 0);
if (m_outbuf.size()) ++m_num_timeouts;
if (m_num_timeouts > m_sm->num_resends())