Michal Hocko writes:

I am not really sure I agree here though. Swappiness has been
traditionally more about workload because it has been believed that it
is a preference of the workload whether the anonymous or disk based
memory is more important. Whether this is a good interface is debatable
of course but time has shown that it is extremely hard to tune.

Sure, it can theoretically be hardware- and workload-specific -- I don't think 
we disagree here. The reason I suggest it's a generally hardware-specific 
tunable rather than a workload-specific tunable is it's pretty rare to see 
anyone who's meaningfully used it for workload-specific tuning :-)