[ruby-core:112460] [Ruby master Feature#19443] Cache `Process.pid`

Issue #19443 has been updated by ko1 (Koichi Sasada).


> However as of glibc version 2.25 the PID cache is removed and calls to getpid() always invoke the actual system call which significantly degrades the performance of existing applications.

Could you show the some benchmark results with/without your patch.
As I understand `getpid()` system call is well tuned so I surprised that there is an impact on the app.

----------------------------------------
Feature #19443: Cache `Process.pid`
https://bugs.ruby-lang.org/issues/19443#change-101904

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
----------------------------------------
It's not uncommon for database client and similar network libraries to protect themselves from Process.fork by regularly checking Process.pid

Until recently most libc would cache `getpid()` so this was a cheap check to make.

However as of glibc version 2.25 the PID cache is removed and calls to `getpid()` always invoke the actual system call which significantly degrades the performance of existing applications.

The reason glibc removed the cache is that some libraries were bypassing `fork(2)` by issuing system calls themselves, causing stale cache issues.

That isn't a concern for Ruby as bypassing MRI's primitive for forking would render the VM unusable, so we can safely cache the PID.

An example of the issue: https://github.com/rails/rails/issues/47418


Patch: https://github.com/ruby/ruby/pull/7326



-- 
https://bugs.ruby-lang.org/
 ______________________________________________
 ruby-core mailing list -- [e-mail]
 To unsubscribe send an email to [e-mail]
 ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/