From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id 283226B0005 for ; Thu, 11 Aug 2016 05:41:14 -0400 (EDT) Received: by mail-wm0-f70.google.com with SMTP id l4so2077373wml.0 for ; Thu, 11 Aug 2016 02:41:14 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id i7si1612322wjo.244.2016.08.11.02.41.12 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 11 Aug 2016 02:41:12 -0700 (PDT) Subject: Re: [PATCH 1/5] mm/debug_pagealloc: clean-up guard page handling code References: <1470809784-11516-1-git-send-email-iamjoonsoo.kim@lge.com> <1470809784-11516-2-git-send-email-iamjoonsoo.kim@lge.com> <20160810081453.GB573@swordfish> From: Vlastimil Babka Message-ID: <172b4c63-b519-cf1d-ed68-1f85f2caed14@suse.cz> Date: Thu, 11 Aug 2016 11:41:12 +0200 MIME-Version: 1.0 In-Reply-To: <20160810081453.GB573@swordfish> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Sergey Senozhatsky , js1304@gmail.com Cc: Andrew Morton , Minchan Kim , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Joonsoo Kim On 08/10/2016 10:14 AM, Sergey Senozhatsky wrote: >> @@ -1650,18 +1655,15 @@ static inline void expand(struct zone *zone, struct page *page, >> size >>= 1; >> VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]); >> >> - if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC) && >> - debug_guardpage_enabled() && >> - high < debug_guardpage_minorder()) { >> - /* >> - * Mark as guard pages (or page), that will allow to >> - * merge back to allocator when buddy will be freed. >> - * Corresponding page table entries will not be touched, >> - * pages will stay not present in virtual address space >> - */ >> - set_page_guard(zone, &page[size], high, migratetype); >> + /* >> + * Mark as guard pages (or page), that will allow to >> + * merge back to allocator when buddy will be freed. >> + * Corresponding page table entries will not be touched, >> + * pages will stay not present in virtual address space >> + */ >> + if (set_page_guard(zone, &page[size], high, migratetype)) >> continue; >> - } > > so previously IS_ENABLED(CONFIG_DEBUG_PAGEALLOC) could have optimized out > the entire branch -- no set_page_guard() invocation and checks, right? but > now we would call set_page_guard() every time? No, there's a !CONFIG_DEBUG_PAGEALLOC version of set_page_guard() that returns false (static inline), so this whole if will be eliminated by the compiler, same as before. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org