From: "nobu (Nobuyoshi Nakada) via ruby-core" <ruby-core@...>
Date: 2023-02-25T09:04:39+00:00
Subject: [ruby-core:112595] [Ruby master Feature#19465] [PATCH] reuse open(2) from rb_file_load_ok on POSIX-like system

Issue #19465 has been updated by nobu (Nobuyoshi Nakada).





Seems fine.����



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

Feature #19465: [PATCH] reuse open(2) from rb_file_load_ok on POSIX-like system

https://bugs.ruby-lang.org/issues/19465#change-102042



* Author: normalperson (Eric Wong)

* Status: Open

* Priority: Normal

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

```

When loading Ruby source files, we can save the result of

successful opens as open(2)/openat(2) are a fairly expensive

syscalls.  This also avoids a time-of-check-to-time-of-use

(TOCTTOU) problem.



This reduces open(2) syscalls during `require'; but should be

most apparent when users have a small $LOAD_PATH.  Users with

large $LOAD_PATH will benefit less since there'll be more

open(2) failures due to ENOENT.



With `strace -c -e openat ruby -e exit' under Linux, this

results in a ~14% reduction of openat(2) syscalls

(glibc uses openat(2) to implement open(2)).



 % time     seconds  usecs/call     calls    errors syscall

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

   0.00    0.000000           0       296       110 openat

   0.00    0.000000           0       254       110 openat



Additionally, the introduction of `struct ruby_file_load_state'

may make future optimizations more apparent.



This change cannot benefit binary (.so) loading since the

dlopen(3) API requires a filename and I'm not aware of an

alternative that takes a pre-existing FD.  In typical

situations, Ruby source files outnumber the mount of .so

files.





I've only tested this lightly on small apps since I don't have

large codebases to test on.  However, I think organizing various

on-stack variables into `struct ruby_file_load_state' can be

beneficial if we end up using io-uring on Linux.

```





---Files--------------------------------

0001-reuse-open-2-from-rb_file_load_ok-on-POSIX-like-syst.patch (15.2 KB)





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