Re: Interesting analysis of linux kernel threading by IBM

From: Davide Libenzi (davidel@maticad.it)
Date: Wed Jan 19 2000 - 12:14:22 EST


Wednesday, January 19, 2000 5:05 PM
 James A Simmons <jsimmons@acsu.buffalo.edu> wrote :
> I read it. It was a excellent paper. I'm amazed by just rearranging the
> data in task_struct it reduces the time in the schedular up to 30% on
> Pentium II. I have the patch included below. Anyone working on a
> many-to-many model for threads for linux?

Hi guys,

I've seen the article made by Ray Bryant with Bill Hartner about scheduler
performance.
On June 1999 I posted a scheduler patch that instead do a linear scan of the
runnable task list,
it "slotify" tasks based on its goodness.
With "only" 300 tasks it'll give me an 80% faster times.
Is my thought that this patch must be included inside the scheduler since it
gives higher performances
with a lot of tasks and a 15 % less with 2 tasks ( at the same amount of
switches / second ).
The fact is that 2 tasks makes a lower switches / second than 300, therefore
the 15% less is relative to a very lower time, so it can be quantified as
about the same performance.
Say that 2 tasks make 10% of switches / second relative to 300 tasks, the 2
tasks case give a lower
performance of about 1.5 % or less.
Now, given the fastest performance with an increasing number of processes,
and given that the number of
tasks a Linux machine must handle today ( SMP, IBM S39 port , etc ... ) I
think that this patch can be useful.
Let me know Your thought about.

Cheers,
    Davide Libenzi.

--
Debian, the freedom in freedom.

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