github-mirror/fish-shell
github-mirror/fish-shell
2
0
Fork 0
mirror of https://github.com/fish-shell/fish-shell.git synced 2025-02-21 14:13:41 +08:00
Code Issues Actions Packages Projects Releases Wiki Activity

Optimize ASSERT_IS_NOT_FORKED_CHILD()

Browse Source 
Use `pthread_atfork()` to mark child processes as dirty when `fork()` is
invoked rather than needing to call into the kernel each time
`ASSERT_IS_NOT_FORKED_CHILD()` is called.

This makes simple test cases that hit `ASSERT_IS_NOT_FORKED_CHILD()` 1.8x faster.

                        ------------------------

With a7998c4829a80269bcd6af941812e35c86bf49e2 reverted but before this optimization:

```
mqudsi@ZBOOK ~/r/fish-shell> hyperfine -S build/fish 'for i in (seq 100000); test 1 = 1; end'
Benchmark #1: for i in (seq 100000); test 1 = 1; end

  Time (mean ± σ):     717.8 ms ±  14.9 ms    [User: 503.4 ms, System: 216.2 ms]
  Range (min … max):   692.3 ms … 740.2 ms
```

With a7998c4829a80269bcd6af941812e35c86bf49e2 reverted and with this optimization:

```
mqudsi@ZBOOK ~/r/fish-shell> hyperfine -S build/fish 'for i in (seq 100000); test 1 = 1; end'
Benchmark #1: for i in (seq 100000); test 1 = 1; end

  Time (mean ± σ):     397.2 ms ±  22.3 ms    [User: 322.1 ms, System: 79.3 ms]
  Range (min … max):   376.0 ms … 444.0 ms
```

Without a7998c4829a80269bcd6af941812e35c86bf49e2 reverted and with this optimization:

mqudsi@ZBOOK ~/r/fish-shell> hyperfine -S build/fish 'for i in (seq 100000); test 1 = 1; end'
Benchmark #1: for i in (seq 100000); test 1 = 1; end

  Time (mean ± σ):     423.4 ms ±  51.6 ms    [User: 363.2 ms, System: 61.3 ms]
  Range (min … max):   378.4 ms … 541.1 ms
```
This commit is contained in:
Mahmoud Al-Qudsi 2018-12-30 19:39:59 -06:00
parent 840619197e
commit 8dddc62aeb
1 changed files with 8 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
src/common.cpp
View File

@ -54,7 +54,11 @@ constexpr wint_t NOT_A_WCHAR = static_cast<wint_t>(WEOF);
struct termios shell_modes;
/// This allows us to determine if we're running on the main thread
static std::atomic<size_t> thread_id { 0 };
/// This allows us to notice when we've forked.
static bool is_forked_proc = false;
/// This allows us to bypass the main thread checks
static bool thread_asserts_cfg_for_testing = false;
wchar_t ellipsis_char;
@ -2171,20 +2175,13 @@ void set_main_thread() {
void configure_thread_assertions_for_testing() { thread_asserts_cfg_for_testing = true; }
bool is_forked_child() {
// Just bail if nobody's called setup_fork_guards, e.g. some of our tools.
if (!initial_pid) return false;
bool is_child_of_fork = (getpid() != initial_pid);
if (is_child_of_fork) {
debug(0, L"Uh-oh: getpid() != initial_pid: %d != %d\n", getpid(), initial_pid);
while (1) sleep(10000);
}
return is_child_of_fork;
return is_forked_proc;
}
void setup_fork_guards() {
// Notice when we fork by stashing our pid. This seems simpler than pthread_atfork().
initial_pid = getpid();
pthread_atfork(nullptr, nullptr, []() {
is_forked_proc = true;
});
}
void save_term_foreground_process_group() {