0003942: More detailed specification of the behaviour of Unix.select - MantisBT

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ID

Project

Category

View Status

Date Submitted

Last Update

0003942

OCaml

OCaml general

public

2005-12-30 17:09

2006-01-18 17:37

Reporter

mottl

Assigned To

Priority

normal

Severity

feature

Reproducibility

N/A

Status

acknowledged

Resolution

open

Platform

OS

OS Version

Product Version

3.09.0

Target Version

Fixed in Version

Summary

0003942: More detailed specification of the behaviour of Unix.select

Description

According to the C-implementation of "Unix.select", file descriptors in ready sets are returned in the reverse order in which they appeared in the argument lists. Could this please be explicitly specified as a guarantee in the documentation?

This way the user may be able to find out much more quickly (in O(1)) whether I/O is possible on a particular descriptor in a large set by simply making it the last one in the argument list and checking the first returned descriptor for equivalence.

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Notes
(0003495) doligez (manager) 2006-01-05 14:19	IMO, if you want to know whether I/O is possible on a particular descriptor, the proper solution is to call select with only that descriptor.

(0003513) mottl (reporter) 2006-01-18 17:37	The reason why this is not a good solution for us is, because we are implementing a messaging library that should have very low latency and very high throughput (> 100000 msgs/sec). System calls are extremely expensive and even just one superfluous call more quite noticably lowers throughput. Unfortunately, Linux still doesn't have a reasonable implementation of asynchronous I/O, which would be the optimum solution for this problem.

Issue History
Date Modified	Username	Field	Change
2005-12-30 17:09	mottl	New Issue
2006-01-05 14:19	doligez	Note Added: 0003495
2006-01-05 14:19	doligez	Severity	text => feature
2006-01-05 14:19	doligez	Status	new => acknowledged
2006-01-18 17:37	mottl	Note Added: 0003513

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