If we have malloced_size() available, then avoid rounding up the string

to the next (guessed) plausible alignment size, and instead find out
how much memory was actually allocated, so that we can set this in the
scalar's SvLEN(). This way, sv_grow() will be called far less often.

p4raw-id: //depot/perl@33377

diff --git a/sv.c b/sv.c
index be66ac8..11e7739 100644 (file)
--- a/sv.c
+++ b/sv.c
@@ -1479,15 +1479,10 @@ Perl_sv_grow(pTHX_ register SV *const sv, register STRLEN newlen)
        s = SvPVX_mutable(sv);
 
     if (newlen > SvLEN(sv)) {          /* need more room? */
+#ifndef MYMALLOC
        newlen = PERL_STRLEN_ROUNDUP(newlen);
-       if (SvLEN(sv) && s) {
-#ifdef MYMALLOC
-           const STRLEN l = malloced_size((void*)SvPVX_const(sv));
-           if (newlen <= l) {
-               SvLEN_set(sv, l);
-               return s;
-           } else
 #endif
+       if (SvLEN(sv) && s) {
            s = (char*)saferealloc(s, newlen);
        }
        else {
@@ -1497,7 +1492,14 @@ Perl_sv_grow(pTHX_ register SV *const sv, register STRLEN newlen)
            }
        }
        SvPV_set(sv, s);
+#ifdef MYMALLOC
+       /* Do this here, do it once, do it right, and then we will never get
+          called back into sv_grow() unless there really is some growing
+          needed.  */
+       SvLEN_set(sv, malloced_size(s));
+#else
         SvLEN_set(sv, newlen);
+#endif
     }
     return s;
 }