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construct/include/ircd/ctx/prof.h

100 lines
3.6 KiB
C++

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