From: Eric Wong <normalperson@...>
Date: 2014-01-04T00:26:50+00:00
Subject: [ruby-core:59542] Re: [ruby-trunk - Feature #9362][Assigned] Minimize cache misshit to gain optimal speed

Eric Wong <normalperson@yhbt.net> wrote:
> 3 bits for embedded array/struct length does not seem to be enough :<

Six bits is enough for 32-bit and 64-byte cache line sizes.  Hopefully
not clobbering anything else that's important... Still building the
rest (this is a slow VM).

Fwiw, we should probably be clamping objects at 64-bytes for now in
case cache lines get bigger.  I no longer have access to any machine
with 128-byte cache lines.

--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -898,7 +898,8 @@ struct RArray {
 };
 #define RARRAY_EMBED_FLAG FL_USER1
 /* FL_USER2 is for ELTS_SHARED */
-#define RARRAY_EMBED_LEN_MASK (FL_USER6|FL_USER7|FL_USER8)
+#define RARRAY_EMBED_LEN_MASK \
+  (FL_USER6|FL_USER7|FL_USER8|FL_USER9|FL_USER10|FL_USER11)
 #define RARRAY_EMBED_LEN_SHIFT (FL_USHIFT+6)
 #define RARRAY_LEN(a) \
     ((RBASIC(a)->flags & RARRAY_EMBED_FLAG) ? \
@@ -1098,7 +1099,8 @@ struct RStruct {
 	const VALUE ary[RSTRUCT_EMBED_LEN_MAX];
     } as;
 };
-#define RSTRUCT_EMBED_LEN_MASK (FL_USER3|FL_USER2|FL_USER1)
+#define RSTRUCT_EMBED_LEN_MASK \
+	(FL_USER6|FL_USER5|FL_USER4|FL_USER3|FL_USER2|FL_USER1)
 #define RSTRUCT_EMBED_LEN_SHIFT (FL_USHIFT+1)
 #define RSTRUCT_LEN(st) \
     ((RBASIC(st)->flags & RSTRUCT_EMBED_LEN_MASK) ? \