Re: relatime: update once per day patches (was: ext3 IO latencymeasurements)

[Andrew Morton]

On Thu, 26 Mar 2009 09:14:28 -0700 (PDT) Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> 
> 
> On Thu, 26 Mar 2009, Andrew Morton wrote:
> > 
> > Hard-wiring a 24-hour interval into the core VFS for all mounted
> > filesystems is dumb.
> 
> Umm. 
> 
> I generally agree witht he "leave policy to user space" people, but this 
> is an area where (a) user space has shown itself to not get it right (ie 
> people don't do even the existing relatime because distros don't) and (b) 
> what's the alternative?
> 
> > I (and others) pointed out that it would be better to implement this as
> > a mount option.  That suggestion was met with varying sillinesses and
> > that is where things stand.
> 
> I'd suggest first just doing the 24 hour thing, and then, IF user space 
> actually ever gets its act together, and people care, and they _ask_ for a 
> mount option, that's when it's worth doing.
> 

We wouldn't normally just enable the new feature by default because it
changes kernel behaviour.  Userspace needs to be changed in some manner to
opt-in.  One way it's `mount -o remount', the other way it's a poke in
/proc.



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