linux-kernel - Re: SUNRPC problem with 2.6.26 and beyond - try again with response in correct place.

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Message-ID: <48FFAF6F.3040406@atmos.washington.edu>
Date:	Wed, 22 Oct 2008 15:55:43 -0700
From:	Harry Edmon <harry@...os.washington.edu>
To:	Trond Myklebust <trond.myklebust@....uio.no>
CC:	linux-kernel@...r.kernel.org
Subject: Re: SUNRPC problem with 2.6.26 and beyond - try again with response
 in correct place.

Trond Myklebust wrote:
> On Wed, 2008-10-22 at 08:35 -0700, Harry Edmon wrote:
>   
>> I have a dual quad-core Xeon system running software 
>> (http://www.unidata.ucar.edu/software/ldm) that relays and processes 
>> weather data through RPC calls, keeping a queue of data in a memory 
>> mapped file.  Up until 2.6.26 the system has run just fine (for example 
>> 2.6.25.17).  But starting with 2.6.26 through 2.6.27.2 the system runs 
>> into a problem after approximately 24 hours.  The symptom is that the 
>> processing slows down to a crawl.  Using "top" I can see that the System 
>> time is up over 90%, with almost no User and Wait time.  If I stop and 
>> restart the software, most of the time it gets better - but sometimes it 
>> takes a reboot to fix the problem.  I have an identical system that does 
>> just processing and ingesting data from remote systems, and it does not 
>> have this problem.  I have tried a number of different kernel 
>> configurations, but they all show the same problem.
>>
>> I suspect a problem with SUNRPC.  I notice that there were a large 
>> number of SUNRPC patches in 2.6.26.  I am looking for suggestions on how 
>> to pin down which patches are causing the problem.  Are there ways to 
>> figure where in the  kernel the time is being spent?  I am will to work 
>> on isolating the problem, but I need some suggestions on the best way to 
>> do it given the large number of SUNRPC patches in 2.6.26 and the fact 
>> that each experiment takes a day.
>>     
>
> The kernel sunrpc interface is not exported to user land: the glibc code
> uses its own, entirely separate implementation of sunrpc.
>
> I cannot therefore see, how your application's RPC calls can be affected
> by kernel sunrpc changes.
>
> Cheers
>   Trond
>
>   
Then how do you explain the the large system time used with 2.6.26 and 
beyond?  Is it some other patch I should be looking at?
-- 

 Dr. Harry Edmon			E-MAIL: harry@...os.washington.edu
 206-543-0547				harry@...hington.edu
 Dept of Atmospheric Sciences		FAX:	206-543-0308
 University of Washington, Box 351640, Seattle, WA 98195-1640

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