transmission/libtransmission/bandwidth.cc

360 lines
9.7 KiB
C++

// This file Copyright © 2008-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <algorithm>
#include <utility> // std::swap()
#include <vector>
#include <fmt/core.h>
#include "transmission.h"
#include "bandwidth.h"
#include "crypto-utils.h" // tr_rand_int_weak()
#include "log.h"
#include "peer-io.h"
#include "tr-assert.h"
#include "utils.h" // tr_time_msec()
/***
****
***/
tr_bytes_per_second_t tr_bandwidth::getSpeedBytesPerSecond(RateControl& r, unsigned int interval_msec, uint64_t now)
{
if (now == 0)
{
now = tr_time_msec();
}
if (now != r.cache_time_)
{
uint64_t bytes = 0;
uint64_t const cutoff = now - interval_msec;
for (int i = r.newest_; r.date_[i] > cutoff;)
{
bytes += r.size_[i];
if (--i == -1)
{
i = HistorySize - 1; /* circular history */
}
if (i == r.newest_)
{
break; /* we've come all the way around */
}
}
r.cache_val_ = static_cast<tr_bytes_per_second_t>(bytes * 1000U / interval_msec);
r.cache_time_ = now;
}
return r.cache_val_;
}
void tr_bandwidth::notifyBandwidthConsumedBytes(uint64_t const now, RateControl* r, size_t size)
{
if (r->date_[r->newest_] + GranularityMSec >= now)
{
r->size_[r->newest_] += size;
}
else
{
if (++r->newest_ == HistorySize)
{
r->newest_ = 0;
}
r->date_[r->newest_] = now;
r->size_[r->newest_] = size;
}
/* invalidate cache_val*/
r->cache_time_ = 0;
}
/***
****
***/
tr_bandwidth::tr_bandwidth(tr_bandwidth* parent)
{
this->setParent(parent);
}
/***
****
***/
static void remove_child(std::vector<tr_bandwidth*>& v, tr_bandwidth* remove_me) noexcept
{
// the list isn't sorted -- so instead of erase()ing `it`,
// do the cheaper option of overwriting it with the final item
if (auto it = std::find(std::begin(v), std::end(v), remove_me); it != std::end(v))
{
*it = v.back();
v.resize(v.size() - 1);
}
}
void tr_bandwidth::deparent() noexcept
{
if (parent_ == nullptr)
{
return;
}
remove_child(parent_->children_, this);
parent_ = nullptr;
}
void tr_bandwidth::setParent(tr_bandwidth* new_parent)
{
TR_ASSERT(this != new_parent);
deparent();
if (new_parent != nullptr)
{
#ifdef TR_ENABLE_ASSERTS
TR_ASSERT(new_parent->parent_ != this);
auto& children = new_parent->children_;
TR_ASSERT(std::find(std::begin(children), std::end(children), this) == std::end(children)); // not already there
#endif
new_parent->children_.push_back(this);
this->parent_ = new_parent;
}
}
/***
****
***/
void tr_bandwidth::allocateBandwidth(
tr_priority_t parent_priority,
tr_direction dir,
unsigned int period_msec,
std::vector<std::shared_ptr<tr_peerIo>>& peer_pool)
{
tr_priority_t const priority = std::max(parent_priority, this->priority_);
/* set the available bandwidth */
if (this->band_[dir].is_limited_)
{
uint64_t const next_pulse_speed = this->band_[dir].desired_speed_bps_;
this->band_[dir].bytes_left_ = next_pulse_speed * period_msec / 1000U;
}
/* add this bandwidth's peer, if any, to the peer pool */
if (auto shared = this->peer_.lock(); shared)
{
shared->priority = priority;
peer_pool.push_back(std::move(shared));
}
// traverse & repeat for the subtree
for (auto* child : this->children_)
{
child->allocateBandwidth(priority, dir, period_msec, peer_pool);
}
}
void tr_bandwidth::phaseOne(std::vector<tr_peerIo*>& peer_array, tr_direction dir)
{
/* First phase of IO. Tries to distribute bandwidth fairly to keep faster
* peers from starving the others. Loop through the peers, giving each a
* small chunk of bandwidth. Keep looping until we run out of bandwidth
* and/or peers that can use it */
tr_logAddTrace(fmt::format("{} peers to go round-robin for {}", peer_array.size(), dir == TR_UP ? "upload" : "download"));
auto n = peer_array.size();
while (n > 0)
{
int const i = tr_rand_int_weak(n); /* pick a peer at random */
// value of 3000 bytes chosen so that when using µTP we'll send a full-size
// frame right away and leave enough buffered data for the next frame to go
// out in a timely manner.
static auto constexpr Increment = size_t{ 3000 };
auto const bytes_used = peer_array[i]->flush(dir, Increment);
tr_logAddTrace(fmt::format("peer #{} of {} used {} bytes in this pass", i, n, bytes_used));
if (bytes_used != Increment)
{
// peer is done writing for now; move it to the end of the list
std::swap(peer_array[i], peer_array[n - 1]);
--n;
}
}
}
void tr_bandwidth::allocate(tr_direction dir, unsigned int period_msec)
{
TR_ASSERT(tr_isDirection(dir));
// keep these peers alive for the scope of this function
auto refs = std::vector<std::shared_ptr<tr_peerIo>>{};
auto high = std::vector<tr_peerIo*>{};
auto low = std::vector<tr_peerIo*>{};
auto normal = std::vector<tr_peerIo*>{};
/* allocateBandwidth () is a helper function with two purposes:
* 1. allocate bandwidth to b and its subtree
* 2. accumulate an array of all the peerIos from b and its subtree. */
this->allocateBandwidth(TR_PRI_LOW, dir, period_msec, refs);
for (auto& io : refs)
{
io->flushOutgoingProtocolMsgs();
switch (io->priority)
{
case TR_PRI_HIGH:
high.push_back(io.get());
[[fallthrough]];
case TR_PRI_NORMAL:
normal.push_back(io.get());
[[fallthrough]];
default:
low.push_back(io.get());
}
}
/* First phase of IO. Tries to distribute bandwidth fairly to keep faster
* peers from starving the others. Loop through the peers, giving each a
* small chunk of bandwidth. Keep looping until we run out of bandwidth
* and/or peers that can use it */
phaseOne(high, dir);
phaseOne(normal, dir);
phaseOne(low, dir);
/* Second phase of IO. To help us scale in high bandwidth situations,
* enable on-demand IO for peers with bandwidth left to burn.
* This on-demand IO is enabled until (1) the peer runs out of bandwidth,
* or (2) the next tr_bandwidth::allocate () call, when we start over again. */
for (auto& io : refs)
{
io->setEnabled(dir, io->hasBandwidthLeft(dir));
}
}
/***
****
***/
unsigned int tr_bandwidth::clamp(uint64_t now, tr_direction dir, unsigned int byte_count) const
{
TR_ASSERT(tr_isDirection(dir));
if (this->band_[dir].is_limited_)
{
byte_count = std::min(byte_count, this->band_[dir].bytes_left_);
/* if we're getting close to exceeding the speed limit,
* clamp down harder on the bytes available */
if (byte_count > 0)
{
if (now == 0)
{
now = tr_time_msec();
}
auto const current = this->getRawSpeedBytesPerSecond(now, TR_DOWN);
auto const desired = this->getDesiredSpeedBytesPerSecond(TR_DOWN);
auto const r = desired >= 1 ? double(current) / desired : 0;
if (r > 1.0)
{
byte_count = 0;
}
else if (r > 0.9)
{
byte_count = static_cast<unsigned int>(byte_count * 0.8);
}
else if (r > 0.8)
{
byte_count = static_cast<unsigned int>(byte_count * 0.9);
}
}
}
if (this->parent_ != nullptr && this->band_[dir].honor_parent_limits_ && byte_count > 0)
{
byte_count = this->parent_->clamp(now, dir, byte_count);
}
return byte_count;
}
void tr_bandwidth::notifyBandwidthConsumed(tr_direction dir, size_t byte_count, bool is_piece_data, uint64_t now)
{
TR_ASSERT(tr_isDirection(dir));
Band* band = &this->band_[dir];
if (band->is_limited_ && is_piece_data)
{
band->bytes_left_ -= std::min(size_t{ band->bytes_left_ }, byte_count);
}
#ifdef DEBUG_DIRECTION
if (dir == DEBUG_DIRECTION && band_->isLimited)
{
fprintf(
stderr,
"%p consumed %5zu bytes of %5s data... was %6zu, now %6zu left\n",
this,
byte_count,
is_piece_data ? "piece" : "raw",
oldBytesLeft,
band_->bytesLeft);
}
#endif
notifyBandwidthConsumedBytes(now, &band->raw_, byte_count);
if (is_piece_data)
{
notifyBandwidthConsumedBytes(now, &band->piece_, byte_count);
}
if (this->parent_ != nullptr)
{
this->parent_->notifyBandwidthConsumed(dir, byte_count, is_piece_data, now);
}
}
/***
****
***/
tr_bandwidth_limits tr_bandwidth::getLimits() const
{
tr_bandwidth_limits limits;
limits.up_limit_KBps = tr_toSpeedKBps(this->getDesiredSpeedBytesPerSecond(TR_UP));
limits.down_limit_KBps = tr_toSpeedKBps(this->getDesiredSpeedBytesPerSecond(TR_DOWN));
limits.up_limited = this->isLimited(TR_UP);
limits.down_limited = this->isLimited(TR_DOWN);
return limits;
}
void tr_bandwidth::setLimits(tr_bandwidth_limits const* limits)
{
this->setDesiredSpeedBytesPerSecond(TR_UP, tr_toSpeedBytes(limits->up_limit_KBps));
this->setDesiredSpeedBytesPerSecond(TR_DOWN, tr_toSpeedBytes(limits->down_limit_KBps));
this->setLimited(TR_UP, limits->up_limited);
this->setLimited(TR_DOWN, limits->down_limited);
}