Minor changes after review

ocaml · Jan 20, 2021 · fc7b0b8 · fc7b0b8
1 parent 1d1ed65
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diff --git a/Changes b/Changes
@@ -14,6 +14,11 @@ Working version
   including the search path for shared stub libraries.
   (David Allsopp, review by Xavier Leroy)
 
+- #9934: Optimise sweeping using prefetching.
+  (Stephen Dolan and Will Hasenplaugh, review by David Allsopp, Xavier
+   Leroy and Damien Doligez, benchmarking by Shubham Kumar and KC
+   Sivaramakrishnan)
+
 - #10025: Track custom blocks (e.g. Bigarray) with Statmemprof
   (Stephen Dolan, review by Leo White, Gabriel Scherer and Jacques-Henri
    Jourdan)

diff --git a/runtime/caml/misc.h b/runtime/caml/misc.h
@@ -118,6 +118,7 @@ CAMLdeprecated_typedef(addr, char *);
 #ifdef CAML_INTERNALS
 #if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
 #define caml_prefetch(p) __builtin_prefetch((p), 1, 3)
+/* 1 = intent to write; 3 = all cache levels */
 #else
 #define caml_prefetch(p)
 #endif

diff --git a/runtime/major_gc.c b/runtime/major_gc.c
@@ -706,7 +706,7 @@ static void sweep_slice (intnat work)
   limit = sweep_chunk + Chunk_size(sweep_chunk);
   while (work > 0){
     if (sweep_hp < limit){
-      caml_prefetch(sweep_hp + 4096);
+      caml_prefetch(sweep_hp + 4000);
       hp = sweep_hp;
       hd = Hd_hp (hp);
       work -= Whsize_hd (hd);