linux-kernel - Re: READDIRPLUS max mount option

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Date:	Fri, 07 Mar 2008 16:04:05 -0500
From:	Kyle Rose <krose@...se.org>
To:	Trond Myklebust <trond.myklebust@....uio.no>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-nfs@...r.kernel.org
Subject: Re: READDIRPLUS max mount option


> The size of the actual READDIRPLUS requests is completely unaffected by
> your patch. Your change actually means that the client will continue to
> use READDIRPLUS on very large directories instead of falling back to
> readdir.
>   
Sorry to be imprecise.  "Size of request" should be "size of response" 
or "cost of request".  The meaning is clear, I think.
> If you want a faster readdir(), you will find that splitting those huge
> directories up into smaller subdirs is an alternative solution that
> tends to scale much better on both client and server.
>   
Agreed that this is probably the least terrible of the available 
solutions, but in my specific case it requires a more extensive 
modification to my software than the relatively minor kernel change.
> Having hundreds of mount options for minor tweaks is not an acceptable
> practice. Each mount option needs to be abundantly justified.
>   
Regarding your straw man, nobody's proposing hundreds of mount options.  
I imagine the effort required to implement each one would keep such a 
thing from happening. ;-)
> Since we're talking about what is really a quite arbitrary limit, I can
> certainly see an argument for why we might want a way to change it, but
> I'm still not convinced that we need to be setting this parameter at the
> mountpoint level.
Fair enough.  A proc entry to alter this globally would be an acceptable 
compromise for me, even if my local sysadmins might not like it.

Kyle
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