On Wed, Sep 10, 2014 at 01:15:15AM -0400, Valdis.Kletnieks@xxxxxx wrote: > On Tue, 09 Sep 2014 16:21:14 -0700, Andrew Morton said: > > On Tue, 9 Sep 2014 23:25:28 +0200 (CEST) Jiri Kosina <jkosina@xxxxxxx> wrote: > > kfree() is quite a hot path to which this will add overhead. And we > > have (as far as we know) no code which will actually use this at > > present. > > We already do a check for ZERO_SIZE_PTR, and given that dereferencing *that* is > instant death for the kernel, and we see it very rarely, I'm going to guess > that IS_ERR(ptr) *has* to be true more often than ZERO_SIZE_PTR, and thus even > more advantageous to short-circuit. ZERO_SIZE_PTR is sort of common. ZERO_SIZE_PTR is an mm abstraction and kfree() and ksize() are basically the only places where we need to test for it. Also friends of kfree() like jbd2_journal_free_transaction(). regards, dan carpenter -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>