Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757944AbaLJRc1 (ORCPT ); Wed, 10 Dec 2014 12:32:27 -0500 Received: from mail-wg0-f47.google.com ([74.125.82.47]:58501 "EHLO mail-wg0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755924AbaLJRc0 (ORCPT ); Wed, 10 Dec 2014 12:32:26 -0500 MIME-Version: 1.0 In-Reply-To: References: <20141210163017.092096069@linux.com> <20141210163033.717707217@linux.com> Date: Wed, 10 Dec 2014 19:32:25 +0200 X-Google-Sender-Auth: 5XXepQdRU1dY6DrWmolFHcTKDB0 Message-ID: Subject: Re: [PATCH 3/7] slub: Do not use c->page on free From: Pekka Enberg To: Christoph Lameter Cc: akpm , Steven Rostedt , LKML , Thomas Gleixner , "linux-mm@kvack.org" , iamjoonsoo@lge.com, Jesper Dangaard Brouer Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 10, 2014 at 7:08 PM, Christoph Lameter wrote: >> > +{ >> > + long d = p - page->address; >> > + >> > + return d > 0 && d < (1 << MAX_ORDER) && d < (compound_order(page) << PAGE_SHIFT); >> > +} >> >> Can you elaborate on what this is doing? I don't really understand it. > > Checks if the pointer points to the slab page. Also it tres to avoid > having to call compound_order needlessly. Not sure if that optimization is > worth it. Aah, it's the (1 << MAX_ORDER) optimization that confused me. Perhaps add a comment there to make it more obvious? I'm fine with the optimization: Reviewed-by: Pekka Enberg - Pekka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/