Avoid false sharing in Hashtbl benchmark

Author: polytypic

dune-project

@@ -16,5 +16,6 @@
  (synopsis "Compositional lock-free data structures and primitives for communication and synchronization")
  (depends
   (kcas (= :version))
-  (mdx (and (>= 1.10.0) :with-test))))
+  (mdx (and (>= 1.10.0) :with-test))
+  (multicore-magic (and (>= 1.0.0) :with-test))))
 (using mdx 0.2)

kcas_data.opam

@@ -11,6 +11,7 @@ depends: [
   "dune" {>= "3.3"}
   "kcas" {= version}
   "mdx" {>= "1.10.0" & with-test}
+  "multicore-magic" {>= "1.0.0" & with-test}
   "odoc" {with-doc}
 ]
 build: [

test/kcas_data/dune

@@ -7,7 +7,7 @@
 (test
  (name hashtbl_bench)
  (modules hashtbl_bench)
- (libraries kcas kcas_data unix)
+ (libraries kcas kcas_data unix multicore-magic)
  (package kcas_data))
 
 (test

test/kcas_data/hashtbl_bench.ml

@@ -7,15 +7,18 @@ module Int = struct
 end
 
 let bench ~n_domains ~n_ops ~n_keys ~percent_read =
-  let t = Hashtbl.create ~hashed_type:(module Int) () in
+  let t =
+    Hashtbl.create ~hashed_type:(module Int) ()
+    |> Multicore_magic.copy_as_padded
+  in
 
   for i = 0 to n_keys - 1 do
     Hashtbl.replace t i i
   done;
 
   let barrier = Atomic.make n_domains in
 
-  let n_ops_todo = Atomic.make n_ops in
+  let n_ops_todo = Atomic.make n_ops |> Multicore_magic.copy_as_padded in
   let rec alloc_ops () =
     let n = Atomic.get n_ops_todo in
     if n = 0 then 0