fs: improve `readFileSync` with file descriptors #49691

anonrig · 2023-09-17T20:47:19Z

This particular change applies to: fs.readFileSync(fs.openSync(__filename), 'utf8')

My local benchmarks are as follows:

fs/readFileSync.js n=10000 hasFileDescriptor='false' path='existing' encoding='undefined'                     0.73 %       ±1.65% ±2.20% ±2.86%
fs/readFileSync.js n=10000 hasFileDescriptor='false' path='existing' encoding='utf8'                          0.05 %       ±1.74% ±2.32% ±3.02%
fs/readFileSync.js n=10000 hasFileDescriptor='false' path='non-existing' encoding='undefined'        ***     62.27 %       ±2.82% ±3.77% ±4.95%
fs/readFileSync.js n=10000 hasFileDescriptor='false' path='non-existing' encoding='utf8'             ***     60.93 %       ±2.72% ±3.64% ±4.78%
fs/readFileSync.js n=10000 hasFileDescriptor='true' path='existing' encoding='undefined'                      0.22 %       ±1.47% ±1.96% ±2.56%
fs/readFileSync.js n=10000 hasFileDescriptor='true' path='existing' encoding='utf8'                  ***     88.18 %       ±2.56% ±3.43% ±4.49%
fs/readFileSync.js n=10000 hasFileDescriptor='true' path='non-existing' encoding='undefined'                 -3.31 %       ±4.32% ±5.80% ±7.65%
fs/readFileSync.js n=10000 hasFileDescriptor='true' path='non-existing' encoding='utf8'                      -3.18 %       ±3.58% ±4.79% ±6.30%

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1413

rluvaton · 2023-09-18T06:34:59Z

Benchmark CI:
https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1397/

bnoordhuis · 2023-09-18T10:16:45Z

Test failures look related.

Correctness issue: file descriptors are int32, not uint32 (also on Windows, because they go through libuv.)

anonrig · 2023-09-18T14:34:02Z

@bnoordhuis We validate file descriptors on lib/fs.js by checking if it is Uint32 (ref: https://github.com/nodejs/node/blob/main/lib/fs.js#L204).

bnoordhuis · 2023-09-18T19:35:42Z

Apparently that goes back to commit 0803962 from 2015... still wrong though. :-)

(Mostly harmless although technically signed integer overflow is UB in C++.)

anonrig · 2023-09-18T19:41:21Z

still wrong though. :-)

Nice find! I'll update the pull request.

@RafaelGSS I'm getting some weird failed test cases where stdout and stderr are both empty in the failing cases, but returning a status of 1. Any idea?

AssertionError [ERR_ASSERTION]
    at Object.<anonymous> (/Users/runner/work/node/node/test/parallel/test-permission-fs-read.js:42:10)
    at Module._compile (node:internal/modules/cjs/loader:1264:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1318:10)
    at Module.load (node:internal/modules/cjs/loader:1113:32)
    at Module._load (node:internal/modules/cjs/loader:954:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:80:12)
    at node:internal/main/run_main_module:23:47 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: null,
  expected: 0,
  operator: 'strictEqual'
}

src/node_file.cc

anonrig · 2023-09-24T20:51:21Z

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1413

09:17:21                                                                                               confidence improvement accuracy (*)    (**)   (***)
09:17:21 fs/readFileSync.js n=10000 hasFileDescriptor='false' path='existing' encoding='undefined'                    -2.80 %       ±8.78% ±11.68% ±15.21%
09:17:21 fs/readFileSync.js n=10000 hasFileDescriptor='false' path='existing' encoding='utf8'                         -6.68 %       ±9.49% ±12.63% ±16.44%
09:17:21 fs/readFileSync.js n=10000 hasFileDescriptor='false' path='non-existing' encoding='undefined'                -3.47 %       ±9.74% ±12.97% ±16.88%
09:17:21 fs/readFileSync.js n=10000 hasFileDescriptor='false' path='non-existing' encoding='utf8'                     -5.20 %       ±8.47% ±11.26% ±14.66%
09:17:21 fs/readFileSync.js n=10000 hasFileDescriptor='true' path='existing' encoding='undefined'                     -1.99 %       ±4.82%  ±6.41%  ±8.34%
09:17:21 fs/readFileSync.js n=10000 hasFileDescriptor='true' path='existing' encoding='utf8'                  ***    126.70 %      ±16.25% ±21.75% ±28.56%
09:17:21 fs/readFileSync.js n=10000 hasFileDescriptor='true' path='non-existing' encoding='undefined'                 -1.31 %       ±6.23%  ±8.29% ±10.79%
09:17:21 fs/readFileSync.js n=10000 hasFileDescriptor='true' path='non-existing' encoding='utf8'              ***    143.95 %      ±18.72% ±25.19% ±33.36%

nodejs-github-bot · 2023-09-24T20:54:23Z

CI: https://ci.nodejs.org/job/node-test-pull-request/54200/

anonrig · 2023-09-24T20:56:57Z

@nodejs/cpp-reviewers @nodejs/fs Can you review?

bnoordhuis · 2023-09-25T07:02:27Z

src/node_file.cc

+      CHECK_EQ(0, uv_fs_close(nullptr, &req, file, nullptr));
+      FS_SYNC_TRACE_END(close);
+    }
+    uv_fs_req_cleanup(&req);


For correctness reasons this ought to be done after the uv_fs_read() call on line 2590. It works okay now because libuv doesn't allocate for a single buffer (i.e. this cleanup call is a no-op) but that's a lucky accident.

Does that mean that on every while loop iteration (for uv_fs_read), we need to call uv_fs_req_cleanup?

resolved

nodejs-github-bot · 2023-09-25T21:56:05Z

Landed in f16f41c

targos · 2023-09-26T06:44:26Z

@anonrig Please always post the benchmark CI results in the PR (for example by editing the comment with the link like I just did). Jenkins results are not permanent.

PR-URL: #49691 Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>

PR-URL: nodejs#49691 Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>

Fix a file permissions regression when `fs.readFileSync()` is called in append mode on a file that does not already exist introduced by the fast path for utf8 encoding. PR-URL: #52101 Fixes: #52079 Refs: #49691 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Vinícius Lourenço Claro Cardoso <contact@viniciusl.com.br> Reviewed-By: Yagiz Nizipli <yagiz.nizipli@sentry.io>

Fix a file permissions regression when `fs.readFileSync()` is called in append mode on a file that does not already exist introduced by the fast path for utf8 encoding. PR-URL: nodejs#52101 Fixes: nodejs#52079 Refs: nodejs#49691 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Vinícius Lourenço Claro Cardoso <contact@viniciusl.com.br> Reviewed-By: Yagiz Nizipli <yagiz.nizipli@sentry.io>

Fix a file permissions regression when `fs.readFileSync()` is called in append mode on a file that does not already exist introduced by the fast path for utf8 encoding. PR-URL: #52101 Fixes: #52079 Refs: #49691 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Vinícius Lourenço Claro Cardoso <contact@viniciusl.com.br> Reviewed-By: Yagiz Nizipli <yagiz.nizipli@sentry.io>

anonrig added the performance Issues and PRs related to the performance of Node.js. label Sep 17, 2023

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. fs Issues and PRs related to the fs subsystem / file system. needs-ci PRs that need a full CI run. labels Sep 17, 2023

anonrig mentioned this pull request Sep 17, 2023

Performance of node:fs nodejs/performance#106

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anonrig force-pushed the fs-read-file-sync-fd branch 2 times, most recently from 0dfcfa4 to de56591 Compare September 18, 2023 19:53

anonrig requested a review from RafaelGSS September 20, 2023 15:06

RafaelGSS previously requested changes Sep 21, 2023

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anonrig requested a review from RafaelGSS September 21, 2023 19:29

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fs: fix file descriptor validator #49752

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anonrig added 2 commits September 24, 2023 16:49

fs: improve readFileSync with file descriptors

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fixup! fs: improve readFileSync with file descriptors

a415654

anonrig force-pushed the fs-read-file-sync-fd branch from 6fea27f to a415654 Compare September 24, 2023 20:49

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nodejs-github-bot merged commit f16f41c into nodejs:main Sep 25, 2023
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ruyadorno pushed a commit that referenced this pull request Sep 28, 2023

fs: improve readFileSync with file descriptors

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PR-URL: #49691 Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>

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v20.7.1 proposal #49917

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fs: improve readFileSync with file descriptors

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PR-URL: #49691 Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>

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v20.8.0 proposal #49932

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binding: mock readFileSync tschaub/mock-fs#378

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Fix tests on Node 20.8.0+ getgauge/gauge-js#603

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fs: improve readFileSync with file descriptors

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PR-URL: nodejs#49691 Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>

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fs: fix edge case in readFileSync utf8 fast path #52101

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fs: improve `readFileSync` with file descriptors #49691

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anonrig commented Sep 17, 2023 •

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fs: improve readFileSync with file descriptors #49691

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fs: improve `readFileSync` with file descriptors #49691

fs: improve `readFileSync` with file descriptors #49691

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