linux-kernel - Re: [PATCH v3 18/68] fscache: Implement cookie user counting and resource pinning

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Date:   Fri, 17 Dec 2021 20:43:48 +0000
From:   David Howells <dhowells@...hat.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     dhowells@...hat.com, linux-cachefs@...hat.com,
        Trond Myklebust <trondmy@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Steve French <sfrench@...ba.org>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Omar Sandoval <osandov@...ndov.com>,
        JeffleXu <jefflexu@...ux.alibaba.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
        linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 18/68] fscache: Implement cookie user counting and resource pinning

Jeff Layton <jlayton@...nel.org> wrote:

> > +unsigned int fscache_lru_cookie_timeout = 10 * HZ;
> >  
> 
> Looks like it only pops after 10s? That's a bit more than the "couple of
> seconds" mentioned in the changelog. In fact, that seems like quite a
> long time.
> 
> Did you arrive at this value empirically somehow?

It was 2s originally, but I upped for some reason I don't remember.  I've left
it as it seems to work, but it is arbitrary.  I should make this configurable
perhaps and/or maybe make it based on the number of cookies on the LRU since
the number of open files is what matters.

I don't have a good heuristic, so I'll just fix the commit message for now.

David