Tom Lane wrote:
I happened to be looking at nodes.h and started wondering just how sane this coding really is:extern PGDLLIMPORT Node *newNodeMacroHolder; #define newNode(size, tag) \ ( \ AssertMacro((size) >= sizeof(Node)), /* need the tag, at least */ \ newNodeMacroHolder = (Node *) palloc0fast(size), \ newNodeMacroHolder->type = (tag), \ newNodeMacroHolder \ ) Given that we're calling palloc, it's not clear that saving one level of function call is really buying much; and what it's costing us is a store to a global variable that the compiler has no way to optimize away. On a lot of platforms, accessing global variables isn't especially cheap. Also, considering that palloc0fast is a nontrivial macro, and that there are a LOT of uses of newNode(), we're paying rather a lot of code space for a pretty dubious savings.
Note that the MemSetLoop macro used in palloc0fast is supposed to be evaluated at compile time, so the code space taken by that macro isn't that big. Turning newNode into function would force it to be evaluated at run-time instead.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
