RE: Why do threads take so long to wake up underlinux

[Veda Narayanan]

All,

     I agree with jim. We need to share information about this as this have direct impact on java/linux combination as a Enterprise platform. This should be addressed in a broad spectrum than just changing a parameter in kernel, though I'm interested in the kernel tweak.

 

    Lets post this question to linux mailing list.

 

Reg

Ved

-----Original Message-----
From: Jim Hazen [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, February 19, 2002 11:49 AM
To: Blackdown
Subject: Re: Why do threads take so long to wake up underlinux

Why not have this discussion on this list?  It seems to directly impact Java.  The relationship between the Linux scheduler and Java is pretty important.  IBM has produced some scheduler kernel mods to improve JVM performance.  These are a bit more complicated than just cranking some params, but none the less should be talked about.  Sure the nitty gritty of 2.5.x changes should probably be discussed elsewhere, but a more related discussion would be...

How do the RT changes in 2.5.x improve JVM performance?  What numbers are people seeing?  With asynchronous multiplexed IO support in 1.4 how do these simple param tweaks effect performance?  Are we seeing much better response times due to busy waiting on selectors?  Are there other issues?  If there are, what are they and how can we design Java code around (for) them?

It seems to me that as people start to design more applications in Java, they will need to discuss issues such as these.  With some of the NIO capabilities in 1.4, some people have suggested pure Java production databases, RT messaging systems, etc.  I for one want to know that there is an issue with the Linux scheduler and how to fix it, if waiting 10ms to send my JMS message is just too long then the pros and cons of tweaking the kernel should be discussed.

-Jim

Generally better responsiveness is caused by a higher chance that
scheduler will sonner finish schedule interactive jobs - because time
quantums are 10 times smaller thus especially CPU hangry applications
like jave will see benefit of this as long computationaly intensive
threads will be more frequently interrupted by small interactive tasks.
The problem is that current linux scheduler is not optimal 
(2.5.X kernels now has O(1) scheduler and some realtime patches which
should improve throughput of the system)

But as I said most probably this is not discussion which should be 
on this list.

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