linux-kernel - Re: [PATCH] sysctl: vfs_cache

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Message-ID: <46043A66.7030102@oracle.com>
Date:	Fri, 23 Mar 2007 13:36:54 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Kyle Moffett <mrmacman_g4@....com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, "J.H." <warthog9@...nel.org>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sysctl: vfs_cache_divisor

Kyle Moffett wrote:
> On Mar 21, 2007, at 19:11:40, Andrew Morton wrote:
>> On Wed, 21 Mar 2007 16:01:32 -0700 Randy Dunlap 
>> <randy.dunlap@...cle.com> wrote:
>>> I prefer the fixed-point values for pressure and dirty* to having 
>>> duplicated entries for each of them.  I'll proceed with that idea.
>>
>> Problem is, if a read of /proc/sys/vm/dirty_ratio is changed to return 
>> 7.457 then existing userspace might get confused.
>>
>> This might be acceptable if we are careful to ensure that reads of 
>> /proc/sys/vm/dirty_ratio will always return an integer if it was 
>> previously initialised with an integer.
> 
> What about instead adding support for fractions (IE: "1/1000") in 
> /proc/sys/vm/dirty_ratio?  If the denominator is 100, the default, then 
> it prints in the form "$NUMERATOR", otherwise it prints answers of the 
> form "$NUMERATOR/$DENOMINATOR".  Input could be of either form, with the 
> kernel auto-setting the denominator to 100 if none is specified.

Hi,
That makes a lot of sense to me.  It gives us finer-grained control
without having to support fixed-point data.

I've been working on the fixed-point data patch, but I'm going to give
this method some time also, to see how it looks in code (instead of just
thinking about it).

Thanks.
-- 
~Randy
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