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Kernel+Profiler: Make profiling per-process and without core dumps

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This patch merges the profiling functionality in the kernel with the
performance events mechanism. A profiler sample is now just another
perf event, rather than a dedicated thing.

Since perf events were already per-process, this now makes profiling
per-process as well.

Processes with perf events would already write out a perfcore.PID file
to the current directory on death, but since we may want to profile
a process and then let it continue running, recorded perf events can
now be accessed at any time via /proc/PID/perf_events.

This patch also adds information about process memory regions to the
perfcore JSON format. This removes the need to supply a core dump to
the Profiler app for symbolication, and so the "profiler coredump"
mechanism is removed entirely.

There's still a hard limit of 4MB worth of perf events per process,
so this is by no means a perfect final design, but it's a nice step
forward for both simplicity and stability.

Fixes #4848
Fixes #4849
This commit is contained in:
Andreas Kling 2021-01-11 09:52:18 +01:00
parent f259d96871
commit 5dafb72370
20 changed files with 195 additions and 310 deletions
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16
Kernel/Scheduler.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -28,8 +28,8 @@
#include <AK/ScopeGuard.h>
#include <AK/TemporaryChange.h>
#include <AK/Time.h>
#include <Kernel/PerformanceEventBuffer.h>
#include <Kernel/Process.h>
#include <Kernel/Profiling.h>
#include <Kernel/RTC.h>
#include <Kernel/Scheduler.h>
#include <Kernel/Time/TimeManagement.h>
@ -477,15 +477,9 @@ void Scheduler::timer_tick(const RegisterState& regs)
if (!is_bsp)
return; // TODO: This prevents scheduling on other CPUs!
if (current_thread->process().is_profiling()) {
SmapDisabler disabler;
auto backtrace = current_thread->raw_backtrace(regs.ebp, regs.eip);
auto& sample = Profiling::next_sample_slot();
sample.pid = current_thread->process().pid();
sample.tid = current_thread->tid();
sample.timestamp = TimeManagement::the().uptime_ms();
for (size_t i = 0; i < min(backtrace.size(), Profiling::max_stack_frame_count); ++i) {
sample.frames[i] = backtrace[i];
}
ASSERT(current_thread->process().perf_events());
auto& perf_events = *current_thread->process().perf_events();
[[maybe_unused]] auto rc = perf_events.append(PERF_EVENT_SAMPLE, 0, 0);
}
if (current_thread->tick((regs.cs & 3) == 0))