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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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43
Kernel/FileSystem/ProcFS.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
@ -51,8 +51,8 @@
#include <Kernel/Net/TCPSocket.h>
#include <Kernel/Net/UDPSocket.h>
#include <Kernel/PCI/Access.h>
#include <Kernel/PerformanceEventBuffer.h>
#include <Kernel/Process.h>
#include <Kernel/Profiling.h>
#include <Kernel/Scheduler.h>
#include <Kernel/StdLib.h>
#include <Kernel/TTY/TTY.h>
@ -113,6 +113,7 @@ enum ProcFileType {
FI_PID,
__FI_PID_Start,
FI_PID_perf_events,
FI_PID_vm,
FI_PID_vmobjects,
FI_PID_stacks, // directory
@ -460,35 +461,21 @@ static bool procfs$modules(InodeIdentifier, KBufferBuilder& builder)
return true;
}
static bool procfs$profile(InodeIdentifier, KBufferBuilder& builder)
static bool procfs$pid_perf_events(InodeIdentifier identifier, KBufferBuilder& builder)
{
auto process = Process::from_pid(to_pid(identifier));
if (!process)
return false;
InterruptDisabler disabler;
JsonObjectSerializer object(builder);
object.add("pid", Profiling::pid().value());
object.add("executable", Profiling::executable_path());
if (!process->executable())
return false;
auto array = object.add_array("events");
bool mask_kernel_addresses = !Process::current()->is_superuser();
Profiling::for_each_sample([&](auto& sample) {
auto object = array.add_object();
object.add("type", "sample");
object.add("tid", sample.tid.value());
object.add("timestamp", sample.timestamp);
auto frames_array = object.add_array("stack");
for (size_t i = 0; i < Profiling::max_stack_frame_count; ++i) {
if (sample.frames[i] == 0)
break;
u32 address = (u32)sample.frames[i];
if (mask_kernel_addresses && !is_user_address(VirtualAddress(address)))
address = 0xdeadc0de;
frames_array.add(address);
}
frames_array.finish();
});
array.finish();
object.finish();
return true;
if (!process->perf_events())
return false;
return process->perf_events()->to_json(builder, process->pid(), process->executable()->absolute_path());
}
static bool procfs$net_adapters(InodeIdentifier, KBufferBuilder& builder)
@ -1752,7 +1739,6 @@ ProcFS::ProcFS()
m_entries[FI_Root_uptime] = { "uptime", FI_Root_uptime, false, procfs$uptime };
m_entries[FI_Root_cmdline] = { "cmdline", FI_Root_cmdline, true, procfs$cmdline };
m_entries[FI_Root_modules] = { "modules", FI_Root_modules, true, procfs$modules };
m_entries[FI_Root_profile] = { "profile", FI_Root_profile, false, procfs$profile };
m_entries[FI_Root_sys] = { "sys", FI_Root_sys, true };
m_entries[FI_Root_net] = { "net", FI_Root_net, false };
@ -1770,6 +1756,7 @@ ProcFS::ProcFS()
m_entries[FI_PID_cwd] = { "cwd", FI_PID_cwd, false, procfs$pid_cwd };
m_entries[FI_PID_unveil] = { "unveil", FI_PID_unveil, false, procfs$pid_unveil };
m_entries[FI_PID_root] = { "root", FI_PID_root, false, procfs$pid_root };
m_entries[FI_PID_perf_events] = { "perf_events", FI_PID_perf_events, false, procfs$pid_perf_events };
m_entries[FI_PID_fd] = { "fd", FI_PID_fd, false };
}