From: Nicholas Clark <nick@ccl4.org>
Date: Tue, 7 Mar 2006 19:31:49 +0000 (+0000)
Subject: Two more TODOs for those with C knowledge.
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=98fed0adfc8a6b4cff1d77d3f468d26b27488d51;p=p5sagit%2Fp5-mst-13.2.git

Two more TODOs for those with C knowledge.

p4raw-id: //depot/perl@27406
---

diff --git a/pod/perltodo.pod b/pod/perltodo.pod
index f4f9f59..c87c9a1 100644
--- a/pod/perltodo.pod
+++ b/pod/perltodo.pod
@@ -372,6 +372,31 @@ anyone feeling like exercising their skill with coverage and profiling tools
 might want to determine what ops I<really> are the most commonly used. And in
 turn suggest evictions and promotions to achieve a better F<pp_hot.c>.
 
+=head2 Shrink struct context
+
+In F<cop.h>, we have
+
+    struct context {
+        U32		cx_type;	/* what kind of context this is */
+        union {
+    	struct block	cx_blk;
+    	struct subst	cx_subst;
+        } cx_u;
+    };
+
+There are less than 256 values for C<cx_type>, and the constituent parts
+C<struct block> and C<struct subst> both contain some C<U8> and C<U16> fields,
+so it should be possible to move them to the first word, and share space with
+a C<U8> C<cx_type>, saving 1 word.
+
+=head2 Allocate OPs from arenas
+
+Currently all new OP structures are individually malloc()ed and free()d.
+All C<malloc> implementations have space overheads, and are now as fast as
+custom allocates so it would both use less memory and less CPU to allocate
+the various OP structures from arenas. The SV arena code can probably be
+re-used for this.
+