mirror of
https://github.com/matrix-construct/construct
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124 lines
4.6 KiB
C++
124 lines
4.6 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_CTX_PROF_H
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/// Profiling for the context system.
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///
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/// These facilities provide tools and statistics. The primary purpose here is
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/// to alert developers of unwanted context behavior, in addition to optimizing
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/// the overall performance of the context system.
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///
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/// The original use case is for the embedded database backend. Function calls
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/// are made which may conduct blocking I/O before returning. This will hang the
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/// current userspace context while it is running and thus BLOCK EVERY CONTEXT
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/// in the entire IRCd. Since this is still an asynchronous system, it just
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/// doesn't have callbacks: we do not do I/O without a cooperative yield.
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/// Fortunately there are mechanisms to mitigate this -- but we have to know
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/// for sure. A database call which has been passed over for mitigation may
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/// start doing some blocking flush under load, etc. The profiler will alert
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/// us of this so it doesn't silently degrade performance.
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///
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namespace ircd::ctx::prof
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{
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enum class event :uint8_t;
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struct ticker;
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ulong cycles() noexcept;
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string_view reflect(const event &);
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// totals
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const ticker &get() noexcept;
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const uint64_t &get(const event &);
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// specific context
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const ticker &get(const ctx &c) noexcept;
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const uint64_t &get(const ctx &c, const event &);
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// current slice state
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const ulong &cur_slice_start() noexcept;
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ulong cur_slice_cycles() noexcept;
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// test accessors
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bool slice_exceeded_warning(const ulong &cycles) noexcept;
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bool slice_exceeded_assertion(const ulong &cycles) noexcept;
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bool slice_exceeded_interrupt(const ulong &cycles) noexcept;
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bool stack_exceeded_warning(const size_t &size) noexcept;
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bool stack_exceeded_assertion(const size_t &size) noexcept;
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extern log::log watchdog;
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}
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namespace ircd::ctx::prof::settings
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{
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extern conf::item<double> stack_usage_warning; // percentage
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extern conf::item<double> stack_usage_assertion; // percentage
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extern conf::item<ulong> slice_warning; // Warn when the yield-to-yield cycles exceeds
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extern conf::item<ulong> slice_interrupt; // Interrupt exception when exceeded (not a signal)
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extern conf::item<ulong> slice_assertion; // abort() when exceeded (not a signal, must yield)
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}
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/// Profiling events for marking. These are currently used internally at the
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/// appropriate point to mark(): the user of ircd::ctx has no reason to mark()
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/// these events; this interface is not quite developed for general use yet.
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enum class ircd::ctx::prof::event
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:uint8_t
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{
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SPAWN, // Context spawn requested
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JOIN, // Context join requested
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JOINED, // Context join completed
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ENTER, // Current context entered
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LEAVE, // Current context leaving
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YIELD, // Current context yielding
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CONTINUE, // Current context continuing
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INTERRUPT, // Current context detects interruption
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TERMINATE, // Current context detects termination
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CYCLES, // monotonic counter (rdtsc)
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_NUM_
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};
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/// structure aggregating any profiling related state for a ctx
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struct ircd::ctx::prof::ticker
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{
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// monotonic counters for events
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std::array<uint64_t, num_of<prof::event>()> event {{0}};
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};
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/// Calculate the current reference cycle count (TSC) for the current
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/// execution epoch/slice. This involves one RDTSC sample which is provided
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/// by ircd::prof/ircd::prof::x86 (or for some other platform), and then
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/// subtracting away the prior RDTSC sample which the context system makes
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/// at the start of each execution slice.
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extern inline ulong
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__attribute__((flatten, always_inline, gnu_inline, artificial))
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ircd::ctx::prof::cur_slice_cycles()
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noexcept
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{
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const auto stop(cycles());
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const auto start(cur_slice_start());
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return stop - start;
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}
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/// Sample the current TSC directly with an rdtsc; this is a convenience
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/// wrapper leading to the ircd::prof interface which contains the platform
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/// specific methods to efficiently sample a cycle count.
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///
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/// Developers are advised to obtain cycle counts from this_ctx::cycles()
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/// which accumulates the cycle count for a specific ctx's execution only.
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extern inline ulong
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__attribute__((flatten, always_inline, gnu_inline, artificial))
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ircd::ctx::prof::cycles()
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noexcept
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{
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return ircd::prof::cycles();
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}
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