Bug 16267 - wrong SemaphoreSlim.Wait busy-loop delay when no timeout
Summary: wrong SemaphoreSlim.Wait busy-loop delay when no timeout
Status: RESOLVED FIXED
Alias: None
Product: Class Libraries
Classification: Mono
Component: System ()
Version: master
Hardware: PC Linux
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
URL:
Depends on:
Blocks:
 
Reported: 2013-11-15 11:56 UTC by Maxime Brugidou
Modified: 2015-12-24 15:03 UTC (History)
2 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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Status:
RESOLVED FIXED

Description Maxime Brugidou 2013-11-15 11:56:39 UTC
In SemaphoreSlim.Wait (https://github.com/mono/mono/blob/master/mcs/class/corlib/System.Threading/SemaphoreSlim.cs#L175)

When millisecondsTimeout is at the default -1 value (when no timeout), the handle.WaitOne waits 1msec where it should wait deepSleepTime (20msec). This causes a lot of CPU waste when the semaphore is waiting.

A simple fix is to wait deepSleepTime (20msec) which is the maximum time currently allowed by this semaphore.

More work could be done to improve this logic and optimize this.
Comment 1 Maxime Brugidou 2013-11-15 12:11:07 UTC
https://github.com/mono/mono/pull/810
Comment 2 Miguel de Icaza [MSFT] 2015-12-24 15:03:58 UTC
This was merged.