m5ops: move to factored .h file

Create empty subs for unsupported archs, much less messy for callers.

bst_vs_heap: create

README.adoc

@@ -7415,7 +7415,9 @@ A flexible setup is:
 ....
 arch=aarch64
 cmd="./run -a '$arch' -g -F '/gem5.sh'"
-restore='-l 1 -- --cpu-type=HPI --restore-with-cpu=HPI --caches --l2cache --l1d_size=1024kB --l1i_size=1024kB --l2_size=1024kB --l3_size=1024kB'
+# These cache sizes roughly match the ARM Cortex A75
+# https://en.wikipedia.org/wiki/ARM_Cortex-A75
+restore='-l 1 -- --cpu-type=HPI --restore-with-cpu=HPI --caches --l2cache --l1d_size=128kB --l1i_size=1024kB --l2_size=256kB'
 
 # Generate a checkpoint after Linux boots, using the faster and less detailed CPU.
 # The boot takes a while, be patient young Padawan.
@@ -7702,6 +7704,25 @@ Buildroot built-in libraries, mostly under Libraries > Other:
 
 There are not yet enabled, but it should be easy to so, see: <<add-new-buildroot-packages>>
 
+===== BST vs heap
+
+https://stackoverflow.com/questions/6147242/heap-vs-binary-search-tree-bst/29548834#29548834
+
+Usage:
+
+....
+printf '/bst_vs_heap.out' > data/readfile
+./run -aA -g -F '/gem5.sh'
+./bst-vs-heap > bst_vs_heap.dat
+....
+
+and then feed `bst_vs_heap.dat` into: https://github.com/cirosantilli/cpp-cheat/blob/9d0f77792fc8e55b20b6ee32018761ef3c5a3f2f/cpp/interactive/bst_vs_heap.gnuplot
+
+Sources:
+
+* link:bst-vs-heap[]
+* link:kernel_module/user/bst_vs_heap.cpp[]
+
 ===== OpenMP
 
 Implemented by GCC itself, so just a toolchain configuration, no external libs, and we enable it by default: