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f1a34d297f
Priority is another property that's only relevant for future sched_algorithm implementations. We don't even have an example yet. It's a good candidate for moving to a specific fiber_properties subclass for that specific sched_algorithm implementation.
85 lines
2.3 KiB
C++
85 lines
2.3 KiB
C++
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// Copyright Oliver Kowalke 2013.
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#include "workstealing_round_robin.hpp"
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#include <boost/assert.hpp>
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#ifdef BOOST_HAS_ABI_HEADERS
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# include BOOST_ABI_PREFIX
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#endif
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workstealing_round_robin::workstealing_round_robin():
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rhead_(0),
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rtail_(&rhead_)
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{}
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void
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workstealing_round_robin::awakened( boost::fibers::fiber_base * f)
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{
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// forward this call to base-class method
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boost::fibers::sched_algorithm_with_properties<affinity>::awakened(f);
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boost::mutex::scoped_lock lk( mtx_);
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// append this fiber_base* to ready queue
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BOOST_ASSERT(! f->nxt_);
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*rtail_ = f;
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rtail_ = &f->nxt_;
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}
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boost::fibers::fiber_base *
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workstealing_round_robin::pick_next()
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{
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boost::mutex::scoped_lock lk( mtx_);
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boost::fibers::fiber_base * f = 0;
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if ( rhead_ )
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{
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f = rhead_;
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// pop head item from ready queue
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rhead_ = rhead_->nxt_;
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f->nxt_ = 0;
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// if that was the last item, reset tail_
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if (! rhead_)
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rtail_ = &rhead_;
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}
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return f;
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}
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boost::fibers::fiber
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workstealing_round_robin::steal() BOOST_NOEXCEPT
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{
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boost::mutex::scoped_lock lk( mtx_);
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// Search the queue for the LAST fiber_base that's willing to migrate,
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// in other words (! thread_affinity).
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boost::fibers::fiber_base ** fp = &rhead_, ** found = 0;
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for ( ; *fp; fp = &(*fp)->nxt_)
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{
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// do not consider any fiber whose thread_affinity is set
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if (! properties(*fp).thread_affinity)
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found = fp;
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}
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if (! found)
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{
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// either the queue is completely empty or all current entries have
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// thread_affinity set
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return boost::fibers::fiber(static_cast<boost::fibers::fiber_base*>(0));
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}
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// We found at least one fiber_base whose thread_affinity is NOT set;
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// *found points to the last of these. Unlink and return it.
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boost::fibers::fiber_base* ret = *found;
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*found = ret->nxt_;
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ret->nxt_ = 0;
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// if that was the last item, reset tail_
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if (! *found)
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rtail_ = &rhead_;
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return boost::fibers::fiber(ret);
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}
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#ifdef BOOST_HAS_ABI_HEADERS
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# include BOOST_ABI_SUFFIX
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#endif
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