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Ruby 3.2 - Speed up rebuilding the loaded feature index and realpath cache #8023

Merged
merged 2 commits into from Jul 29, 2023
Merged

Ruby 3.2 - Speed up rebuilding the loaded feature index and realpath cache #8023

merged 2 commits into from Jul 29, 2023

Commits on Jul 29, 2023

  1. Speed up rebuilding the loaded feature index 

    Rebuilding the loaded feature index slowed down with the bug fix
for #17885 in 79a4484.  The
slowdown was extreme if realpath emulation was used, but even when
not emulated, it could be about 10x slower.

This adds loaded_features_realpath_map to rb_vm_struct. This is a
hidden hash mapping loaded feature paths to realpaths. When
rebuilding the loaded feature index, look at this hash to get
cached realpath values, and skip calling rb_check_realpath if a
cached value is found.

Fixes [Bug #19246]
    @jeremyevans @nagachika
    jeremyevans authored and nagachika committed Jul 29, 2023
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  2. Add a realpath cache to reduce number of syscalls. 

    Number of lstat and stat syscalls for each 'require'd file is doubled,
because rb_realpath_internal is called from two places with the same
arguments in require_internal; once for checking the realpaths cache,
and once in load_iseq_eval when iseq is not found.

Introduce rb_realpath_internal_cached function to reuse the realpath_map
cache which memoizes rb_realpath_internal function, leading to less
syscalls and increased startup performance depending on the cost of the syscalls
in a particular environment.
    @krk @nagachika
    krk authored and nagachika committed Jul 29, 2023
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