Re: vm_dirty_ratio seems a bit large.

[Andrew Morton <akpm@osdl.org>]

Robin Holt <holt@sgi.com> wrote:
>
> > No, you could just extend them to understand fixed point.  Keep
>  > printing integers as integers, print non-integers with one (or two:
>  > will we ever need 0.01% increments?) decimal places.
> 
>  Right now, it is possible to build our largest Altix configuration with
>  64TB of memory (unfortunatetly, we can't get any customers to pay that
>  large of bill ;).  We are currently shipping a few 4TB systems and hope
>  to be selling 20TB systems by the end of the year (at least engineering
>  hopes to).
> 
>  Given that, two decimal places are really not enough.  We probably need
>  at least 3.
> 
>  Is there any reason to not do 3 places?  Is this the right direction to
>  head or does anybody know of problems this would cause?

It's a rather unorthodox fix, but not illogical.  I guess it depends upon
how much sysctl infrastructure it adds.  Probably quite a lot.

Another approach would be to just say the ratio now has a range 0 .. 
999,999 and then, if it happens to be less than 100, treat that as a
percentage for back-compatibility reasons.  Although that's a bit kludgy
and perhaps a completely new /proc entry would be better.