[Guile-commits] 02/02: Bump fluid cache size to 16 entries

[Andy Wingo]

wingo pushed a commit to branch master
in repository guile.

commit 2864f11d3415c650d9e80f8e7787e4df81dcc7e9
Author: Andy Wingo <address@hidden>
Date:   Fri Feb 17 11:01:19 2017 +0100

    Bump fluid cache size to 16 entries
    
    * libguile/cache-internal.h (SCM_CACHE_SIZE): Bump to 16.  It seems that
      a thread accesses more than 8 fluids by default (%stacks, the
      exception handler, current ports, current-fiber, port read/write
      waiters) which leads every fiber to cause cache eviction and copying
      the value table, which is a bottleneck.  Instead just bump this cache
      size.
      (scm_cache_lookup): Update unrolled search.
---
 libguile/cache-internal.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libguile/cache-internal.h b/libguile/cache-internal.h
index fc1e3c1..4c1732f 100644
--- a/libguile/cache-internal.h
+++ b/libguile/cache-internal.h
@@ -39,7 +39,7 @@ struct scm_cache_entry
   scm_t_bits value;
 };
 
-#define SCM_CACHE_SIZE 8
+#define SCM_CACHE_SIZE 16
 
 struct scm_cache
 {
@@ -81,6 +81,7 @@ scm_cache_lookup (struct scm_cache *cache, SCM k)
   scm_t_bits k_bits = SCM_UNPACK (k);
   struct scm_cache_entry *entry = cache->entries;
   /* Unrolled binary search, compiled to branchless cmp + cmov chain.  */
+  if (entry[8].key <= k_bits) entry += 8;
   if (entry[4].key <= k_bits) entry += 4;
   if (entry[2].key <= k_bits) entry += 2;
   if (entry[1].key <= k_bits) entry += 1;