module: skip directories known not to exist by bnoordhuis · Pull Request #9196 · nodejs/node · GitHub

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

CI: https://ci.nodejs.org/job/node-test-pull-request/4587/

LGTM

Here is what the access pattern looked liked before this pull request. (File paths shortened for brevity.)

29754 stat(".../node_modules/finalhandler", 0x7fff639476d0) = -1 ENOENT (No such file or directory)
29754 stat(".../node_modules/finalhandler.js", 0x7fff63947630) = -1 ENOENT (No such file or directory)
29754 stat(".../node_modules/finalhandler.json", 0x7fff63947630) = -1 ENOENT (No such file or directory)
29754 stat(".../node_modules/finalhandler.node", 0x7fff63947630) = -1 ENOENT (No such file or directory)
29754 open(".../node_modules/finalhandler/package.json", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
29754 stat(".../node_modules/finalhandler/index.js", 0x7fff63947630) = -1 ENOENT (No such file or directory)
29754 stat(".../node_modules/finalhandler/index.json", 0x7fff63947630) = -1 ENOENT (No such file or directory)
29754 stat(".../node_modules/finalhandler/index.node", 0x7fff63947630) = -1 ENOENT (No such file or directory)

Note how the last four are guaranteed to fail because of the first one.

LGTM

Does attempting to require from a directory, failing and making a new directory, writing into, and then loading files from that directory still work?

You say 'still' but does it work now? The stat cache persists for the duration of a module's top-level code.

strictEqual?
I know equal is consistent with the rest of the test but updating the test may be worthwhile

I followed the style of the surrounding code here.

EDIT: Never mind, didn't see you edited your comment. Still, consistency is important, right?

I'll update the test en bloc in a separate pull request.

EDIT: #9263

LGTM with a nit

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>

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>

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>

Verify that a package.json without a .main property loads index.js. PR-URL: #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>

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: #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>

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: #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 should this be backported?

It could but it doesn't have to be. It's an optimization, not a bug fix.

@bnoordhuis @MylesBorins should be labelled either dont-land-on-v6.x or backport-requested-to-v6.x, what say you? I think making v6.x faster is good, but not essential.

It should be a zero-risk back-port but then again, no one complained it's slow. The most compelling reason would be to avoid future merge conflicts but OTOH, lib/module.js doesn't see all that many updates so probably not much of an issue. /stream-of-consciousness

Don't bother, it's fine.

I think we should just keep this labelled and be ready to backport if we run into problems in the future... would prefer not to touch module

nodejs-github-bot added the module Issues and PRs related to the module subsystem. label Oct 19, 2016

silverwind approved these changes Oct 19, 2016

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evanlucas approved these changes Oct 19, 2016

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cjihrig approved these changes Oct 20, 2016

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jasnell reviewed Oct 20, 2016

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bnoordhuis added 3 commits October 24, 2016 22:48

bnoordhuis force-pushed the skip-enoent-module-dirs branch from 8f5dfbc to 678c094 Compare October 24, 2016 20:51

bnoordhuis closed this Oct 24, 2016

bnoordhuis deleted the skip-enoent-module-dirs branch October 24, 2016 20:51

bnoordhuis merged commit 678c094 into nodejs:master Oct 24, 2016

evanlucas mentioned this pull request Nov 3, 2016

v7.1.0 proposal - 2016-11-08 #9438

Merged

MylesBorins added lts-watch-v4.x labels Nov 17, 2016

MylesBorins added dont-land-on-v4.x and removed lts-watch-v4.x labels Mar 9, 2017

MylesBorins added the baking-for-lts PRs that need to wait before landing in a LTS release. label May 8, 2017

MylesBorins removed the baking-for-lts PRs that need to wait before landing in a LTS release. label Aug 17, 2018

               assert.notEqual(threeFolder, three);
               console.error('test package.json require() loading');
+              assert.equal(require('../fixtures/packages/index').ok, 'ok',

module: skip directories known not to exist by bnoordhuis · Pull Request #9196 · nodejs/node · GitHub

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module: skip directories known not to exist - #9196

module: skip directories known not to exist#9196bnoordhuis merged 3 commits intonodejs:masternodejs/node:masterfrom bnoordhuis:skip-enoent-module-dirsbnoordhuis/io.js:skip-enoent-module-dirsCopy head branch name to clipboard

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module: skip directories known not to exist#9196
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