I am wondering if anybody can try to compile and run this C++11 code of mine for a portable word-based proxy collector, a sort of poor mans RCU, on an ARM based system? I don't have access to one. I am interested in the resulting output.
https://pastebin.com/raw/CYZ78gVj(raw text link, no ads... :^)
_______________________________________
// Chris M. Thomassons Poor Mans RCU... Example 456...
#include <iostream>
#include <atomic>
#include <thread>
#include <cstdlib>
#include <cstdint>
#include <climits>
#include <functional>
// Masks
static constexpr std::uint32_t ct_ref_mask = 0xFFFFFFF0U;
static constexpr std::uint32_t ct_ref_complete = 0x30U;
static constexpr std::uint32_t ct_ref_inc = 0x20U;
static constexpr std::uint32_t ct_proxy_mask = 0xFU;
static constexpr std::uint32_t ct_proxy_quiescent = 0x10U;
// Iteration settings
static constexpr unsigned long ct_reader_iters_n = 2000000;
static constexpr unsigned long ct_writer_iters_n = 200000;
// Thread counts
static constexpr unsigned long ct_reader_threads_n = 53;
static constexpr unsigned long ct_writer_threads_n = 11;
// Some debug/sanity check things...
// Need to make this conditional in compilation with some macros...
static std::atomic<std::uint32_t> g_debug_node_allocations(0);
static std::atomic<std::uint32_t> g_debug_node_deallocations(0);
static std::atomic<std::uint32_t> g_debug_dtor_collect(0);
static std::atomic<std::uint32_t> g_debug_release_collect(0);
static std::atomic<std::uint32_t> g_debug_quiesce_begin(0);
static std::atomic<std::uint32_t> g_debug_quiesce_complete(0);
static std::atomic<std::uint32_t> g_debug_quiesce_complete_nodes(0);
// Need to align and pad data structures! To do...
struct ct_node
{
std::atomic<ct_node*> m_next;
ct_node* m_defer_next;
ct_node() : m_next(nullptr), m_defer_next(nullptr)
{
g_debug_node_allocations.fetch_add(1, std::memory_order_relaxed);
}
~ct_node()
{
g_debug_node_deallocations.fetch_add(1, std::memory_order_relaxed);
}
};
// The proxy collector itself... :^)
template<std::size_t T_defer_limit>
class ct_proxy
{
static std::uint32_t prv_destroy(ct_node* n)
{
std::uint32_t count = 0;
while (n)
{
ct_node* next = n->m_defer_next;
delete n;
count++;
n = next;
}
return count;
}
public:
class collector
{
friend class ct_proxy;
private:
std::atomic<ct_node*> m_defer;
std::atomic<std::uint32_t> m_defer_count;
std::atomic<std::uint32_t> m_count;
public:
collector()
: m_defer(nullptr),
m_defer_count(0),
m_count(0)
{
}
~collector()
{
prv_destroy(m_defer.load(std::memory_order_relaxed));
}
};
private:
std::atomic<std::uint32_t> m_current;
std::atomic<bool> m_quiesce;
ct_node* m_defer;
collector m_collectors[2];
public:
ct_proxy()
: m_current(0),
m_quiesce(false),
m_defer(nullptr)
{
}
~ct_proxy()
{
prv_destroy(m_defer);
}
private:
void prv_quiesce_begin()
{
// Try to begin the quiescence process.
if (! m_quiesce.exchange(true, std::memory_order_acquire))
{
g_debug_quiesce_begin.fetch_add(1, std::memory_order_relaxed);
// advance the current collector and grab the old one.
std::uint32_t old = m_current.load(std::memory_order_relaxed) & ct_proxy_mask;
old = m_current.exchange((old + 1) & 1, std::memory_order_acq_rel);
collector& c = m_collectors[old & ct_proxy_mask];
// decode reference count.
std::uint32_t refs = old & ct_ref_mask;
// increment and generate an odd reference count.
std::uint32_t old_refs = c.m_count.fetch_add(refs + ct_proxy_quiescent, std::memory_order_release);
if (old_refs == 0 - refs)
{
g_debug_dtor_collect.fetch_add(1, std::memory_order_relaxed);
// odd reference count and drop-to-zero condition detected!
prv_quiesce_complete(c);
}
}
}
void prv_quiesce_complete(collector& c)
{
g_debug_quiesce_complete.fetch_add(1, std::memory_order_relaxed);
// the collector `c' is now in a quiescent state! :^)
std::atomic_thread_fence(std::memory_order_acquire);
// maintain the back link and obtain "fresh" objects from
// this collection.
ct_node* n = m_defer;
m_defer = c.m_defer.load(std::memory_order_relaxed);
c.m_defer.store(0, std::memory_order_relaxed);
// reset the reference count.
c.m_count.store(0, std::memory_order_relaxed);
c.m_defer_count.store(0, std::memory_order_relaxed);
// release the quiesce lock.
m_quiesce.store(false, std::memory_order_release);
// destroy nodes.
std::uint32_t count = prv_destroy(n);
g_debug_quiesce_complete_nodes.fetch_add(count, std::memory_order_relaxed);
}
public:
collector& acquire()
{
// increment the master count _and_ obtain current collector.
std::uint32_t current =
m_current.fetch_add(ct_ref_inc, std::memory_order_acquire);
// decode the collector index.
return m_collectors[current & ct_proxy_mask];
}
void release(collector& c)
{
// decrement the collector.
std::uint32_t count =
c.m_count.fetch_sub(ct_ref_inc, std::memory_order_release);
// check for the completion of the quiescence process.
if ((count & ct_ref_mask) == ct_ref_complete)
{
// odd reference count and drop-to-zero condition detected!
g_debug_release_collect.fetch_add(1, std::memory_order_relaxed);
prv_quiesce_complete(c);
}
}
collector& sync(collector& c)
{
// check if the `c' is in the middle of a quiescence process.
if (c.m_count.load(std::memory_order_relaxed) & ct_proxy_quiescent)
{
// drop `c' and get the next collector.
release(c);
return acquire();
}
return c;
}
void collect()
{
prv_quiesce_begin();
}
void collect(collector& c, ct_node* n)
{
if (! n) return;
// link node into the defer list.
ct_node* prev = c.m_defer.exchange(n, std::memory_order_relaxed);
n->m_defer_next = prev;
// bump the defer count and begin quiescence process if over
// the limit.
std::uint32_t count =
c.m_defer_count.fetch_add(1, std::memory_order_relaxed) + 1;
if (count >= (T_defer_limit / 2))
{
prv_quiesce_begin();
}
}
};
typedef ct_proxy<10> ct_proxy_collector;
// you're basic lock-free stack...
// well, minus ABA counter and DWCAS of course! ;^)
class ct_stack
{
std::atomic<ct_node*> m_head;
public:
ct_stack() : m_head(nullptr)
{
}
public:
void push(ct_node* n)
{
ct_node* head = m_head.load(std::memory_order_relaxed);
do
{
n->m_next.store(head, std::memory_order_relaxed);
}
while (! m_head.compare_exchange_weak(
head,
n,
std::memory_order_release));
}
ct_node* flush()
{
return m_head.exchange(nullptr, std::memory_order_acquire);
}
ct_node* get_head()
{
return m_head.load(std::memory_order_acquire);
}
ct_node* pop()
{
ct_node* head = m_head.load(std::memory_order_acquire);
ct_node* xchg;
do
{
if (! head) return nullptr;
xchg = head->m_next.load(std::memory_order_relaxed);
}
while (!m_head.compare_exchange_weak(
head,
xchg,
std::memory_order_acquire));
return head;
}
};
// The shared state
struct ct_shared
{
ct_proxy<10> m_proxy_gc;
ct_stack m_stack;
};
// Reader threads
// Iterates through the lock free stack
void ct_thread_reader(ct_shared& shared)
{
// iterate the lockfree stack
for (unsigned long i = 0; i < ct_reader_iters_n; ++i)
{
ct_proxy_collector::collector& c = shared.m_proxy_gc.acquire();
ct_node* n = shared.m_stack.get_head();
while (n)
{
// need to add in some processing...
// std::this_thread::yield();
n = n->m_next.load(std::memory_order_relaxed);
}
shared.m_proxy_gc.release(c);
}
}
// Writer threads
// Mutates the lock free stack
void ct_thread_writer(ct_shared& shared)
{
for (unsigned long wloop = 0; wloop < 42; ++wloop)
{
shared.m_proxy_gc.collect();
for (unsigned long i = 0; i < ct_writer_iters_n; ++i)
{
shared.m_stack.push(new ct_node());
}
//std::this_thread::yield();
ct_proxy_collector::collector& c = shared.m_proxy_gc.acquire();
for (unsigned long i = 0; i < ct_writer_iters_n; ++i)
{
shared.m_proxy_gc.collect(c, shared.m_stack.pop());
}
shared.m_proxy_gc.release(c);
for (unsigned long i = 0; i < ct_writer_iters_n / 2; ++i)
{
shared.m_proxy_gc.collect();
}
{
ct_proxy_collector::collector& c = shared.m_proxy_gc.acquire();
for (unsigned long i = 0; i < ct_writer_iters_n; ++i)
{
ct_node* n = shared.m_stack.pop();
if (! n) break;
shared.m_proxy_gc.collect(c, n);
}
shared.m_proxy_gc.release(c);
}
if ((wloop % 3) == 0)
{
shared.m_proxy_gc.collect();
}
}
}
int main()
{
std::cout << "Chris M. Thomassons Proxy Collector Port ver .0.0.2...\n";
std::cout << "_______________________________________\n\n";
{
ct_shared shared;
std::thread readers[ct_reader_threads_n];
std::thread writers[ct_writer_threads_n];
std::cout << "Booting threads...\n";
for (unsigned long i = 0; i < ct_writer_threads_n; ++i)
{
writers[i] = std::thread(ct_thread_writer, std::ref(shared));
}
for (unsigned long i = 0; i < ct_reader_threads_n; ++i)
{
readers[i] = std::thread(ct_thread_reader, std::ref(shared));
}
std::cout << "Threads running...\n";
for (unsigned long i = 0; i < ct_reader_threads_n; ++i)
{
readers[i].join();
}
for (unsigned long i = 0; i < ct_writer_threads_n; ++i)
{
writers[i].join();
}
}
std::cout << "Threads completed!\n\n";
// Sanity check!
{
std::uint32_t node_allocations = g_debug_node_allocations.load(std::memory_order_relaxed);
std::uint32_t node_deallocations = g_debug_node_deallocations.load(std::memory_order_relaxed);
std::uint32_t dtor_collect = g_debug_dtor_collect.load(std::memory_order_relaxed);
std::uint32_t release_collect = g_debug_release_collect.load(std::memory_order_relaxed);
std::uint32_t quiesce_complete = g_debug_quiesce_complete.load(std::memory_order_relaxed);
std::uint32_t quiesce_begin = g_debug_quiesce_begin.load(std::memory_order_relaxed);
std::uint32_t quiesce_complete_nodes = g_debug_quiesce_complete_nodes.load(std::memory_order_relaxed);
std::cout << "node_allocations = " << node_allocations << "\n";
std::cout << "node_deallocations = " << node_deallocations << "\n\n";
std::cout << "dtor_collect = " << dtor_collect << "\n";
std::cout << "release_collect = " << release_collect << "\n";
std::cout << "quiesce_complete = " << quiesce_complete << "\n";
std::cout << "quiesce_begin = " << quiesce_begin << "\n";
std::cout << "quiesce_complete_nodes = " << quiesce_complete_nodes << "\n";
if (node_allocations != node_deallocations)
{
std::cout << "OH SHIT! NODE LEAK!!! SHIT! = " << node_allocations - node_deallocations << "\n\n";
}
}
std::cout << "\n\nTest Completed!\n\n";
return 0;
}
_______________________________________
portable proxy collector test...
Re: portable proxy collector test...