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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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10
Kernel/Syscalls/execve.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
@ -29,8 +29,8 @@
#include <AK/TemporaryChange.h>
#include <Kernel/FileSystem/Custody.h>
#include <Kernel/FileSystem/FileDescription.h>
#include <Kernel/PerformanceEventBuffer.h>
#include <Kernel/Process.h>
#include <Kernel/Profiling.h>
#include <Kernel/Random.h>
#include <Kernel/Time/TimeManagement.h>
#include <Kernel/VM/AllocationStrategy.h>
@ -446,7 +446,6 @@ int Process::do_exec(NonnullRefPtr<FileDescription> main_program_description, Ve
return -ENOENT;
// Disable profiling temporarily in case it's running on this process.
bool was_profiling = is_profiling();
TemporaryChange profiling_disabler(m_profiling, false);
// Mark this thread as the current thread that does exec
@ -589,8 +588,9 @@ int Process::do_exec(NonnullRefPtr<FileDescription> main_program_description, Ve
tss.cr3 = m_page_directory->cr3();
tss.ss2 = m_pid.value();
if (was_profiling)
Profiling::did_exec(path);
// Throw away any recorded performance events in this process.
if (m_perf_event_buffer)
m_perf_event_buffer->clear();
{
ScopedSpinLock lock(g_scheduler_lock);