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module: skip directories known not to exist #9196

Merged
merged 3 commits into from
Oct 24, 2016
Merged

module: skip directories known not to exist #9196

merged 3 commits into from
Oct 24, 2016

Commits on Oct 24, 2016

  1. test: add more module loader test coverage 

    Verify that a package.json without a .main property loads index.js.

PR-URL: nodejs#9196
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
    @bnoordhuis
    bnoordhuis committed Oct 24, 2016
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  2. doc: add performance warning to require.extensions 

    Discourage using require.extensions because it slows down the module
loader.  The number of file system operations that the module system
has to perform in order to resolve a `require(...)` statement to a
filename is proportional to the number of registered extensions.

PR-URL: nodejs#9196
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
    @bnoordhuis
    bnoordhuis committed Oct 24, 2016
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  3. module: skip directories known not to exist 

    There is no point in trying to search for files in a directory that
we know does not exist, so stop doing that.

Reduces the total number of stat(2) calls and the number of stat(2)
misses on a medium-sized application by about 21% and 29% respectively.

Reduces the total number of package.json open(2) calls and the number
of open(2) misses by about 21% and 93% (!) respectively.

Before:

    % time     seconds  usecs/call     calls    errors syscall
    ------ ----------- ----------- --------- --------- ----------------
     50.93    0.178419          38      4702           lstat
     29.08    0.101875          36      2800      2010 stat
     11.36    0.039796          43       932       215 open
      5.39    0.018897          34       550           fstat
      3.24    0.011337          34       336           pread
    ------ ----------- ----------- --------- --------- ----------------
    100.00    0.350324                  9320      2225 total

After:

    % time     seconds  usecs/call     calls    errors syscall
    ------ ----------- ----------- --------- --------- ----------------
     55.49    0.176638          38      4702           lstat
     24.76    0.078826          35      2225      1435 stat
     10.19    0.032434          44       733        16 open
      6.19    0.019719          36       550           fstat
      3.37    0.010723          32       336           pread
    ------ ----------- ----------- --------- --------- ----------------
    100.00    0.318340                  8546      1451 total

PR-URL: nodejs#9196
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
    @bnoordhuis
    bnoordhuis committed Oct 24, 2016
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