Message-ID: <40144509.4060300@nmu.edu>
Date: Sun, 25 Jan 2004 17:36:57 -0500
From: Randy Appleton <rappleto@nmu.edu>
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To: Nick Piggin <piggin@cyberone.com.au>
CC: Bill Davidsen <davidsen@tmr.com>, linux-kernel@vger.kernel.org
Subject: Re: Unneeded Code Found??
References: <3FFF3931.4030202@nmu.edu> <4006B998.5040403@tmr.com> <400B2BCF.7090003@nmu.edu> <400B7100.7090600@cyberone.com.au> <40119EC6.9010803@nmu.edu> <4011B586.1090101@cyberone.com.au>
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Nick Piggin wrote:

>
>
> Randy Appleton wrote:
>
>> Nick Piggin wrote: 
>
>
>
>>
>>> Yes it gets used.
>>>
>>> I think its a lot more common with direct io and when you have lots of
>>> processes.
>>
>>
>>
>> I'm not arguing, but how do you know this?  I'm trying to convince 
>> myself that the code is used, and at least on my system
>> a few days of general use, followed by heavy parallel compiles, 
>> doesn't use the code even once.
>>
>> I have not tested direct I/O.  Otherwise it looks unused.
>>
>
> Because I have seen it - I have instrumented it.
>
> Your usage patterns are pretty tame actually. I remember having 100 
> processes
> randomly reading from the same part of the disk was one of my test cases.
> You need direct IO otherwise everything ends up in pagecache.
>
> I haven't seen workloads where it gets used a lot, but that doesn't 
> mean they
> don't exist, and I've never seen the code cause any problems, so there 
> is no
> need to make any trade offs by removing it.
>
O.K.  That's convincing.  Thanks for the time.

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