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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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15
Services/SystemServer/main.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
@ -205,18 +205,6 @@ static void create_tmp_coredump_directory()
umask(old_umask);
}
static void create_tmp_profiler_coredumps_directory()
{
dbgln("Creating /tmp/profiler_coredumps directory");
auto old_umask = umask(0);
auto rc = mkdir("/tmp/profiler_coredumps", 0755);
if (rc < 0) {
perror("mkdir(/tmp/profiler_coredumps)");
ASSERT_NOT_REACHED();
}
umask(old_umask);
}
int main(int, char**)
{
prepare_devfs();
@ -229,7 +217,6 @@ int main(int, char**)
mount_all_filesystems();
create_tmp_rpc_directory();
create_tmp_coredump_directory();
create_tmp_profiler_coredumps_directory();
parse_boot_mode();
Core::EventLoop event_loop;