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/**
* @file threadpool.cpp
* @author Nat Goodspeed
* @date 2021-10-21
* @brief Implementation for threadpool.
*
* $LicenseInfo:firstyear=2021&license=viewerlgpl$
* Copyright (c) 2021, Linden Research, Inc.
* $/LicenseInfo$
*/
// Precompiled header
#include "linden_common.h"
// associated header
#include "threadpool.h"
// STL headers
// std headers
// external library headers
// other Linden headers
#include "commoncontrol.h"
#include "llcoros.h"
#include "llerror.h"
#include "llevents.h"
#include "llsd.h"
#include "stringize.h"
#include <boost/fiber/algo/round_robin.hpp>
/*****************************************************************************
* Custom fiber scheduler for worker threads
*****************************************************************************/
// As of 2022-12-06, each of our worker threads only runs a single (default)
// fiber: we don't launch explicit fibers within worker threads, nor do we
// anticipate doing so. So a worker thread that's simply waiting for incoming
// tasks should really sleep a little. Override the default fiber scheduler to
// implement that.
struct sleepy_robin: public boost::fibers::algo::round_robin
{
virtual void suspend_until( std::chrono::steady_clock::time_point const&) noexcept
{
#if LL_WINDOWS
// round_robin holds a std::condition_variable, and
// round_robin::suspend_until() calls
// std::condition_variable::wait_until(). On Windows, that call seems
// busier than it ought to be. Try just sleeping.
Sleep(1);
#else
// currently unused other than windows, but might as well have something here
// different units than Sleep(), but we actually just want to sleep for any de-minimis duration
usleep(1);
#endif
}
virtual void notify() noexcept
{
// Since our Sleep() call above will wake up on its own, we need not
// take any special action to wake it.
}
};
/*****************************************************************************
* ThreadPoolBase
*****************************************************************************/
LL::ThreadPoolBase::ThreadPoolBase(const std::string& name,
size_t threads,
WorkQueueBase* queue,
bool auto_shutdown):
super(name),
mName("ThreadPool:" + name),
mThreadCount(getConfiguredWidth(name, threads)),
mQueue(queue),
mAutomaticShutdown(auto_shutdown)
{}
void LL::ThreadPoolBase::start()
{
for (size_t i = 0; i < mThreadCount; ++i)
{
std::string tname{ stringize(mName, ':', (i+1), '/', mThreadCount) };
mThreads.emplace_back(tname, [this, tname]()
{
LL_PROFILER_SET_THREAD_NAME(tname.c_str());
run(tname);
});
}
if (!mAutomaticShutdown)
{
// Some threads, like main window's might need to run a bit longer
// to wait for a proper shutdown message
return;
}
// When the app is shutting down, close the queue and join the workers.
mStopListener = LLCoros::getStopListener(
mName,
[this](const LLSD& status)
{
// viewer is starting shutdown -- proclaim the end is nigh!
LL_DEBUGS("ThreadPool") << mName << " saw " << status << LL_ENDL;
close();
});
}
LL::ThreadPoolBase::~ThreadPoolBase()
{
close();
}
void LL::ThreadPoolBase::close()
{
if (! mQueue->isClosed())
{
LL_DEBUGS("ThreadPool") << mName << " closing queue and joining threads" << LL_ENDL;
mQueue->close();
for (auto& pair: mThreads)
{
if (pair.second.joinable())
{
LL_DEBUGS("ThreadPool") << mName << " waiting on thread " << pair.first << LL_ENDL;
pair.second.join();
}
}
LL_DEBUGS("ThreadPool") << mName << " shutdown complete" << LL_ENDL;
}
}
void LL::ThreadPoolBase::run(const std::string& name)
{
#if LL_WINDOWS
// Try using sleepy_robin fiber scheduler.
boost::fibers::use_scheduling_algorithm<sleepy_robin>();
#endif // LL_WINDOWS
LL_DEBUGS("ThreadPool") << name << " starting" << LL_ENDL;
run();
LL_DEBUGS("ThreadPool") << name << " stopping" << LL_ENDL;
}
void LL::ThreadPoolBase::run()
{
mQueue->runUntilClose();
}
//static
size_t LL::ThreadPoolBase::getConfiguredWidth(const std::string& name, size_t dft)
{
LLSD poolSizes;
try
{
poolSizes = LL::CommonControl::get("Global", "ThreadPoolSizes");
// "ThreadPoolSizes" is actually a map containing the sizes of
// interest -- or should be, if this process has an
// LLViewerControlListener instance and its settings include
// "ThreadPoolSizes". If we failed to retrieve it, perhaps we're in a
// program that doesn't define that, or perhaps there's no such
// setting, or perhaps we're asking too early, before the LLEventAPI
// itself has been instantiated. In any of those cases, it seems worth
// warning.
if (! poolSizes.isDefined())
{
// Note: we don't warn about absence of an override key for a
// particular ThreadPool name, that's fine. This warning is about
// complete absence of a ThreadPoolSizes setting, which we expect
// in a normal viewer session.
LL_WARNS("ThreadPool") << "No 'ThreadPoolSizes' setting for ThreadPool '"
<< name << "'" << LL_ENDL;
}
}
catch (const LL::CommonControl::Error& exc)
{
// We don't want ThreadPool to *require* LLViewerControlListener.
// Just log it and carry on.
LL_WARNS("ThreadPool") << "Can't check 'ThreadPoolSizes': " << exc.what() << LL_ENDL;
}
LL_DEBUGS("ThreadPool") << "ThreadPoolSizes = " << poolSizes << LL_ENDL;
// LLSD treats an undefined value as an empty map when asked to retrieve a
// key, so we don't need this to be conditional.
LLSD sizeSpec{ poolSizes[name] };
// We retrieve sizeSpec as LLSD, rather than immediately as LLSD::Integer,
// so we can distinguish the case when it's undefined.
return sizeSpec.isInteger() ? sizeSpec.asInteger() : dft;
}
//static
size_t LL::ThreadPoolBase::getWidth(const std::string& name, size_t dft)
{
auto instance{ getInstance(name) };
if (instance)
{
return instance->getWidth();
}
else
{
return getConfiguredWidth(name, dft);
}
}
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