Re: Containers and /proc/sys/vm/drop_caches

[Dave Hansen <dave-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

On Thu, 2011-01-06 at 13:43 -0800, Matt Helsley wrote:
> That said, the more important question is why should we provide
> drop_caches inside a container? My understanding is it's largely a
> workload-debugging tool and not something meant to truly solve
> problems. If that's the case then we shouldn't provide it at all or it
> should actually interfere with the host cache. 

Yeah, what's the problem that you're solving with drop_caches?  The odds
are, there's a better way.

That said, it _might_ be worth doing things like dropping (inode or
dentry) caches per-sb.  That's a much better fit than using big, ugly,
loosely-defined, system-wide knobs like drop_caches.

Also, unless we start giving containers real ownership of devices or
partitions, it's going to be pretty darn hard to let things clear caches
in a meaningful way.  What if one container wants an object cleared
while another doesn't?

-- Dave