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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
View file

@ -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);

6
Kernel/Syscalls/perf_event.cpp
View file

@ -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
@ -31,9 +31,7 @@ namespace Kernel {
int Process::sys$perf_event(int type, FlatPtr arg1, FlatPtr arg2)
{
if (!m_perf_event_buffer)
m_perf_event_buffer = make<PerformanceEventBuffer>();
return m_perf_event_buffer->append(type, arg1, arg2);
return ensure_perf_events().append(type, arg1, arg2);
}
}

23
Kernel/Syscalls/profiling.cpp
View file

@ -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
@ -25,8 +25,10 @@
*/
#include <Kernel/CoreDump.h>
#include <Kernel/FileSystem/FileDescription.h>
#include <Kernel/FileSystem/VirtualFileSystem.h>
#include <Kernel/PerformanceEventBuffer.h>
#include <Kernel/Process.h>
#include <Kernel/Profiling.h>
namespace Kernel {
@ -41,7 +43,7 @@ int Process::sys$profiling_enable(pid_t pid)
return -ESRCH;
if (!is_superuser() && process->uid() != m_uid)
return -EPERM;
Profiling::start(*process);
process->ensure_perf_events();
process->set_profiling(true);
return 0;
}
@ -54,20 +56,9 @@ int Process::sys$profiling_disable(pid_t pid)
return -ESRCH;
if (!is_superuser() && process->uid() != m_uid)
return -EPERM;
if (!process->is_profiling())
return -EINVAL;
process->set_profiling(false);
Profiling::stop();
// We explicitly unlock here because we can't hold the lock when writing the coredump VFS
lock.unlock();
if (auto coredump = CoreDump::create(*process, String::formatted("/tmp/profiler_coredumps/{}", pid))) {
auto result = coredump->write();
if (result.is_error())
return result.error();
} else {
// FIXME: Return an error maybe?
dbgln("Unable to create profiler coredump for PID {}", pid);
}
return 0;
}