Re: Re: NFS Patch for FSCache

[David Howells <dhowells@redhat.com>]

Troy Benjegerdes <hozer@hozed.org> wrote:

> How big was the cachefs filesystem?

Several Gig. I don't remember how big, but the disk I tried it on is totally
kaput unfortunately.

> Now try reading a 1GB file over nfs..

I'll give that a go at some point. However, I suspect that any size over twice
the amount of pagecache available is going to scale fairly consistently until
you start hitting the lid on the cache. I say twice because firstly you fill
the pagecache with pages and start throwing them at the disk, and then you
have to start on a rolling process of waiting for those to hit the disk before
evicting them from the pagecache, which isn't going to get going smoothly
until you've ejected the original load of pages.

> I have found (with openafs), that I either need a really small cache, or
> a really big one.. The bigger the openafs cache gets, the slower it
> goes. The only place i run with a > 1GB openafs cache is on an imap
> server that has an 8gb cache for maildirs.

What filesystem underlies your OpenAFS cache? OpenAFS doesn't actually do its
own file to disk management within the cache, but uses a host filesystem for
that.

David