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transmission/libtransmission/bandwidth.cc

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// This file Copyright © 2008-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0), GPLv3 (SPDX: GPL-3.0),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <algorithm>
#include <vector>
#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"
#define dbgmsg(...) tr_logAddDeepNamed(nullptr, __VA_ARGS__)
/***
****
***/
unsigned int 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.transfers_[i].date_ > cutoff;)
{
bytes += r.transfers_[i].size_;
if (--i == -1)
{
i = HistorySize - 1; /* circular history */
}
if (i == r.newest_)
{
break; /* we've come all the way around */
}
}
r.cache_val_ = unsigned(bytes * 1000U / interval_msec);
r.cache_time_ = now;
}
return r.cache_val_;
}
void Bandwidth::notifyBandwidthConsumedBytes(uint64_t const now, RateControl* r, size_t size)
{
if (r->transfers_[r->newest_].date_ + GranularityMSec >= now)
{
r->transfers_[r->newest_].size_ += size;
}
else
{
if (++r->newest_ == HistorySize)
{
r->newest_ = 0;
}
r->transfers_[r->newest_].date_ = now;
r->transfers_[r->newest_].size_ = size;
}
/* invalidate cache_val*/
r->cache_time_ = 0;
}
/***
****
***/
Bandwidth::Bandwidth(Bandwidth* new_parent)
{
this->band_[TR_UP].honor_parent_limits_ = true;
this->band_[TR_DOWN].honor_parent_limits_ = true;
this->setParent(new_parent);
}
/***
****
***/
static void remove_child(std::vector<Bandwidth*>& v, Bandwidth* remove_me)
{
auto it = std::find(std::begin(v), std::end(v), remove_me);
if (it == std::end(v))
{
return;
}
// the list isn't sorted -- so instead of erase()ing `it`,
// do the cheaper option of overwriting it with the final item
*it = v.back();
v.resize(v.size() - 1);
}
void Bandwidth::setParent(Bandwidth* new_parent)
{
TR_ASSERT(this != new_parent);
if (this->parent_ != nullptr)
{
remove_child(this->parent_->children_, this);
this->parent_ = nullptr;
}
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 Bandwidth::allocateBandwidth(
tr_priority_t parent_priority,
tr_direction dir,
unsigned int period_msec,
std::vector<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 (this->peer_ != nullptr)
{
this->peer_->priority = priority;
peer_pool.push_back(this->peer_);
}
// traverse & repeat for the subtree
for (auto* child : this->children_)
{
child->allocateBandwidth(priority, dir, period_msec, peer_pool);
}
}
void Bandwidth::phaseOne(std::vector<tr_peerIo*>& peerArray, 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 */
dbgmsg("%lu peers to go round-robin for %s", peerArray.size(), dir == TR_UP ? "upload" : "download");
size_t n = peerArray.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 uTP 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. */
size_t const increment = 3000;
int const bytes_used = tr_peerIoFlush(peerArray[i], dir, increment);
dbgmsg("peer #%d of %zu used %d bytes in this pass", i, n, bytes_used);
if (bytes_used != int(increment))
{
/* peer is done writing for now; move it to the end of the list */
std::swap(peerArray[i], peerArray[n - 1]);
--n;
}
}
}
void Bandwidth::allocate(tr_direction dir, unsigned int period_msec)
{
TR_ASSERT(tr_isDirection(dir));
auto high = std::vector<tr_peerIo*>{};
auto low = std::vector<tr_peerIo*>{};
auto normal = std::vector<tr_peerIo*>{};
auto tmp = 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, tmp);
for (auto* io : tmp)
{
tr_peerIoRef(io);
tr_peerIoFlushOutgoingProtocolMsgs(io);
switch (io->priority)
{
case TR_PRI_HIGH:
high.push_back(io);
[[fallthrough]];
case TR_PRI_NORMAL:
normal.push_back(io);
[[fallthrough]];
default:
low.push_back(io);
}
}
/* 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 Bandwidth::allocate () call, when we start over again. */
for (auto* io : tmp)
{
tr_peerIoSetEnabled(io, dir, tr_peerIoHasBandwidthLeft(io, dir));
}
for (auto* io : tmp)
{
tr_peerIoUnref(io);
}
}
/***
****
***/
unsigned int 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 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);
}
}
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