Re: Volanomark regress on ia64

From: Nick Piggin <nickpiggin_at_yahoo.com.au>
Date: 2005-09-18 20:56:31
Chen, Kenneth W wrote:
> Take a look at http://kernel-perf.sourceforge.net/results.machine_id=26.html
> 
> First chart with volanomark benchmark.  It took ~ 11% performance regression
> on 2.6.13-git9 and 2.6.14-rc1.
> 
> It is not those two particular kernel version have the problem per se.  It
> would've shown on 2.6.13-rc1 when default hz rate was switched to 250.  Last
> week, I happened to audit the system and made the hz switch and the problem
> showed up.
> 
> Hz=1000  cpu idle is about 54%, the raw throughput is 74935 msgs/sec
> Hz=250   cpu idle is about 58%, the raw throughput is 67246 msgs/sec
> 
> I think it has something to do with the scheduler load balance.  While I'm
> looking into schedstat and etc.  Posting here for everyone to pour over the
> issue.
> 
> vmstat/readprofle/schedstat result with 1K hz and 250 hz attached.
> 

Hi Ken,
Made any progress yet?

It looks like the problem is confined to ia64? Are the x86-64 machines
also running with HZ set to 250?

I would look at differences between SD_CPU_INIT for ia64 versus the
generic definition. cache_hot_time and cache_nice_tries by the looks,
both those could cause increased idle time.

Nick

-- 
SUSE Labs, Novell Inc.

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Received on Sun Sep 18 20:56:26 2005

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