rename data_size to approx_size, add fastpath to Thunk affinity

Author: Shashi Gowda

Diff for: src/lib/dumbref.jl

@@ -16,18 +16,18 @@ let token_count = 0
     next_token_id() = (token_count+=1)
 end
 
-function data_size(d)
-    Base.summarysize(d)
+function approx_size(d)
+    Base.summarysize(d) # note: this is accurate but expensive
 end
 
-function data_size(xs::AbstractArray{String})
+function approx_size(xs::AbstractArray{String})
     # doesn't check for redundant references, but
     # really super fast in comparison to summarysize
     sum(map(sizeof, xs))
 end
 
 function make_token(data)
-    sz = data_size(data)
+    sz = approx_size(data)
     tok = MemToken(myid(), next_token_id(), sz)
 
     if !isempty(freeable_lru)

Diff for: src/thunk.jl

@@ -45,7 +45,12 @@ function affinity(t::Thunk)
             end
         end
     end
-    sort!(collect(aff), by=last,rev=true)
+    aff_vec = collect(aff)
+    if length(aff) > 1
+        sort!(aff_vec, by=last,rev=true)
+    else
+        aff_vec
+    end
 end
 
 function delayed(f; kwargs...)