From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30ABFC56201 for ; Thu, 12 Nov 2020 14:38:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4C9A222240 for ; Thu, 12 Nov 2020 14:38:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4C9A222240 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6AADD6B0072; Thu, 12 Nov 2020 09:38:07 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 65B346B0073; Thu, 12 Nov 2020 09:38:07 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5242C6B0074; Thu, 12 Nov 2020 09:38:07 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0136.hostedemail.com [216.40.44.136]) by kanga.kvack.org (Postfix) with ESMTP id 2399F6B0072 for ; Thu, 12 Nov 2020 09:38:07 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id B6FB01EE6 for ; Thu, 12 Nov 2020 14:38:06 +0000 (UTC) X-FDA: 77476020972.07.foot21_4d0e08127307 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id 99F3E1803F9A9 for ; Thu, 12 Nov 2020 14:38:06 +0000 (UTC) X-HE-Tag: foot21_4d0e08127307 X-Filterd-Recvd-Size: 7114 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf01.hostedemail.com (Postfix) with ESMTP for ; Thu, 12 Nov 2020 14:38:06 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AE479AFA7; Thu, 12 Nov 2020 14:38:04 +0000 (UTC) Subject: Re: [PATCH v2 2/5] mm, page_poison: use static key more efficiently To: David Hildenbrand , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alexander Potapenko , Kees Cook , Michal Hocko , Mateusz Nosek , Laura Abbott References: <20201103152237.9853-1-vbabka@suse.cz> <20201103152237.9853-3-vbabka@suse.cz> <796d64ea-5b40-b8a3-fb36-f15708e60d94@redhat.com> From: Vlastimil Babka Message-ID: Date: Thu, 12 Nov 2020 15:37:52 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <796d64ea-5b40-b8a3-fb36-f15708e60d94@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11/11/20 4:38 PM, David Hildenbrand wrote: > On 03.11.20 16:22, Vlastimil Babka wrote: >> Commit 11c9c7edae06 ("mm/page_poison.c: replace bool variable with static key") >> changed page_poisoning_enabled() to a static key check. However, the function >> is not inlined, so each check still involves a function call with overhead not >> eliminated when page poisoning is disabled. >> >> Analogically to how debug_pagealloc is handled, this patch converts >> page_poisoning_enabled() back to boolean check, and introduces >> page_poisoning_enabled_static() for fast paths. Both functions are inlined. >> >> The function kernel_poison_pages() is also called unconditionally and does >> the static key check inside. Remove it from there and put it to callers. Also >> split it to two functions kernel_poison_pages() and kernel_unpoison_pages() >> instead of the confusing bool parameter. >> >> Also optimize the check that enables page poisoning instead of debug_pagealloc >> for architectures without proper debug_pagealloc support. Move the check to >> init_mem_debugging_and_hardening() to enable a single static key instead of >> having two static branches in page_poisoning_enabled_static(). > > [...] > >> + * For use in fast paths after init_mem_debugging() has run, or when a >> + * false negative result is not harmful when called too early. >> + */ >> +static inline bool page_poisoning_enabled_static(void) >> +{ >> + return (static_branch_unlikely(&_page_poisoning_enabled)); > > As already mentioned IIRC: Yes, it was, and I thought I fixed it. Guess not. > return static_branch_unlikely(&_page_poisoning_enabled); > >> +} >> @@ -1260,7 +1271,8 @@ static __always_inline bool free_pages_prepare(struct page *page, >> if (want_init_on_free()) >> kernel_init_free_pages(page, 1 << order); >> >> - kernel_poison_pages(page, 1 << order, 0); >> + if (page_poisoning_enabled_static()) >> + kernel_poison_pages(page, 1 << order); > > This would look much better by having kernel_poison_pages() simply be > implemented in a header, where the static check is performed. > > Take a look at how it's handled in mm/shuffle.h Ok. Fixup below. ----8<---- From 7ce26ba61296f583f0f9089e7887f07424f25d2c Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Thu, 12 Nov 2020 15:20:58 +0100 Subject: [PATCH] mm, page_poison: use static key more efficiently-fix Non-functional cleanups, per David Hildenbrand. Signed-off-by: Vlastimil Babka --- include/linux/mm.h | 16 +++++++++++++--- mm/page_alloc.c | 7 +++---- mm/page_poison.c | 4 ++-- 3 files changed, 18 insertions(+), 9 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 4d6dd9f44571..861b9392b5dc 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2867,8 +2867,8 @@ extern int apply_to_existing_page_range(struct mm_struct *mm, extern void init_mem_debugging_and_hardening(void); #ifdef CONFIG_PAGE_POISONING -extern void kernel_poison_pages(struct page *page, int numpages); -extern void kernel_unpoison_pages(struct page *page, int numpages); +extern void __kernel_poison_pages(struct page *page, int numpages); +extern void __kernel_unpoison_pages(struct page *page, int numpages); extern bool _page_poisoning_enabled_early; DECLARE_STATIC_KEY_FALSE(_page_poisoning_enabled); static inline bool page_poisoning_enabled(void) @@ -2881,7 +2881,17 @@ static inline bool page_poisoning_enabled(void) */ static inline bool page_poisoning_enabled_static(void) { - return (static_branch_unlikely(&_page_poisoning_enabled)); + return static_branch_unlikely(&_page_poisoning_enabled); +} +static inline void kernel_poison_pages(struct page *page, int numpages) +{ + if (page_poisoning_enabled_static()) + __kernel_poison_pages(page, numpages); +} +static inline void kernel_unpoison_pages(struct page *page, int numpages) +{ + if (page_poisoning_enabled_static()) + __kernel_unpoison_pages(page, numpages); } #else static inline bool page_poisoning_enabled(void) { return false; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index fd7f9345adc0..1388b5939551 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1271,8 +1271,8 @@ static __always_inline bool free_pages_prepare(struct page *page, if (want_init_on_free()) kernel_init_free_pages(page, 1 << order); - if (page_poisoning_enabled_static()) - kernel_poison_pages(page, 1 << order); + kernel_poison_pages(page, 1 << order); + /* * arch_free_page() can make the page's contents inaccessible. s390 * does this. So nothing which can access the page's contents should @@ -2281,8 +2281,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order, if (debug_pagealloc_enabled_static()) kernel_map_pages(page, 1 << order, 1); kasan_alloc_pages(page, order); - if (page_poisoning_enabled_static()) - kernel_unpoison_pages(page, 1 << order); + kernel_unpoison_pages(page, 1 << order); set_page_owner(page, order, gfp_flags); } diff --git a/mm/page_poison.c b/mm/page_poison.c index dd7aeada036f..4d75fc9ccc7a 100644 --- a/mm/page_poison.c +++ b/mm/page_poison.c @@ -30,7 +30,7 @@ static void poison_page(struct page *page) kunmap_atomic(addr); } -void kernel_poison_pages(struct page *page, int n) +void __kernel_poison_pages(struct page *page, int n) { int i; @@ -89,7 +89,7 @@ static void unpoison_page(struct page *page) kunmap_atomic(addr); } -void kernel_unpoison_pages(struct page *page, int n) +void __kernel_unpoison_pages(struct page *page, int n) { int i; -- 2.29.1