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fs: readFile in one syscall to avoid context switching #41436

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fs: readFile in one syscall to avoid context switching #41436

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fs: readFile in one syscall to avoid context switching
mmomtchev Jan 7, 2022
ed9590f
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mmomtchev Jan 7, 2022
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4 changes: 1 addition & 3 deletions lib/internal/fs/read_file_context.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,13 +2,11 @@

const {
ArrayPrototypePush,
MathMin,
ReflectApply,
} = primordials;

const {
constants: {
kReadFileBufferLength,
kReadFileUnknownBufferLength,
}
} = require('internal/fs/utils');
Expand Down Expand Up @@ -99,7 +97,7 @@ class ReadFileContext {
} else {
buffer = this.buffer;
offset = this.pos;
length = MathMin(kReadFileBufferLength, this.size - this.pos);
length = this.size - this.pos;
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Suggested change
length = this.size - this.pos;
length = this.signal ? MathMin(kReadFileBufferLength, this.size - this.pos) : this.size - this.pos;

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@mmomtchev mmomtchev Jan 12, 2022 •
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@ronag I am not sure I understand the benefit of this? this.signal won't exist when starting the operation?
In fact, after reading the previous discussion I agree that the current implementation has some very important advantages that must be preserved.
One of them is that it is fair and not prone to starvation - because after this PR if you launch 5 readFile with the current 4 threads you won't start reading the fifth one until the first four are completed.

}

const req = new FSReqCallback();
Expand Down