X fs1: Tune kd so that sizeof(btree data page) is ~= page

name         old time/op    new time/op    delta
IndexLoad-4    2.49ms ± 1%    2.18ms ± 3%  -12.39%  (p=0.000 n=9+10)

name         old alloc/op   new alloc/op   delta
IndexLoad-4    3.77MB ± 0%    3.49MB ± 0%   -7.50%  (p=0.000 n=8+9)

name         old allocs/op  new allocs/op  delta
IndexLoad-4     1.98k ± 0%     0.53k ± 0%  -72.96%  (p=0.000 n=10+10)

t/neo/storage/fs1/fsb/fsbtree.go

@@ -18,7 +18,7 @@ import (
 
 const (
 	kx = 32 //TODO benchmark tune this number if using custom key/value type(s).
-	kd = 32 //TODO benchmark tune this number if using custom key/value type(s).
+	kd = 126
 	//kx = 2
 	//kd = 2
 )

t/neo/storage/fs1/fsb/gen-fsbtree

-#!/bin/sh -e
-# generate b.Tree with compile-time KEY=zodb.Oid, VALUE=int64 and direct oidCmp calls
+#!/bin/bash -e
+# generate b.Tree with compile-time KEY=zodb.Oid, VALUE=int64, tuned kd and direct oidCmp calls
 
 KEY=zodb.Oid
 VALUE=int64
 
+# adjust kd so that sizeof(d) ~= page
+de=16	# KEY+VALUE
+o=24	# d.c, d.n, d.p
+kd=$(( (4096 - $o - $de) / (2 * $de) ))
+
 b=github.com/cznic/b
 Bdir=`go list -f '{{.Dir}}' $b`
 Brev=`cd $Bdir && git describe --always`
@@ -18,6 +23,8 @@ make -s -C $Bdir generic |sed	\
 	-e 's/package b/package fsb/g'	\
 	-e "s/KEY/$KEY/g"	\
 	-e "s/VALUE/$VALUE/g"	\
+ \
+	-e "s/^\(\\s*kd = \).*\$/\\1$kd/g"	\
  \
 	-e '/cmp *Cmp$/d'	\
 	-e 's/t\.cmp(/oidCmp(/g'	\