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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DD7E9C47258 for ; Fri, 2 Feb 2024 08:10:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=0w/0lwHBSzIoMyzKoeZ9AiOd9Jy9fbwPUm9RZyesTic=; b=n9bEuEt6+Up5aV th8sy44I+t/ACVl1ZMcP7Z7WXhGMaOk1hqO03lFWqIhKfwTa7WUJPD+U5SpTN4EDfKNE1fEwLLqKa Fqz0vuSGYErmjfe/q9ATtUVuLCgSUVodHtbJ7ICCnEsnPzF+ttHSPFWSZuQvfGef8SsdrKUfzPGb3 fLQhFOzam4gxyszFAQt/3Kkm0V1PQqSn4fT/U37XdG5BlHme8BOZ1xyF6m3fmkQJeMVcxGTWaXpXy Q+b4h4aIBQu5uX0THQ7syP6P42F3TNmPR/0TVPP82QyZfS8/4AVYwXiYyiVXk8tfQ73GJGq7Rjjch LxWb00scAU/cRlYRS4DQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rVocv-0000000Ah68-34SF; Fri, 02 Feb 2024 08:10:21 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rVoca-0000000Agml-44Jy for linux-arm-kernel@bombadil.infradead.org; Fri, 02 Feb 2024 08:10:00 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Transfer-Encoding:MIME-Version :References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=RG2xpbHo+BZWR1EUw1E88djCi8W1k8Ens4WKUhSzkA8=; b=fqoZfcp99QJ3tJ2FWaL7dyuEjR sWgx0atkuqg7oWz50I0uXj80h0yRyv9Pq+Jb+aFVdJhB4DDlekEbq4hFzKnJ2ESTnM4LbSFffeXca 82BaJSWeqi+gaccEfpvrsRVK7AhrgPtIvB9MYYKUqosZ5TQ0WyETuN4MplxP87UlLrsecv2deSVLT zyQW1vU8A9jZiuRsXxpK7EkuyrSJO5uSVN14bWx3b4IYaI0ww8L30UxlT7uao36UImOUDGDgZEPAp tf07iWGFzh3/P9wIHUt9KwNeVpD+t92Q14aoGE8zF9HV14FnmmEpiB1P6d5YCA+BmkctaqOGcoEHb KaMdCKfA==; Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rVocH-00000009urk-2gCe for linux-arm-kernel@lists.infradead.org; Fri, 02 Feb 2024 08:09:55 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B640A1BD0; Fri, 2 Feb 2024 00:10:22 -0800 (PST) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.26]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CA6BF3F5A1; Fri, 2 Feb 2024 00:09:36 -0800 (PST) From: Ryan Roberts To: Catalin Marinas , Will Deacon , Ard Biesheuvel , Marc Zyngier , James Morse , Andrey Ryabinin , Andrew Morton , Matthew Wilcox , Mark Rutland , David Hildenbrand , Kefeng Wang , John Hubbard , Zi Yan , Barry Song <21cnbao@gmail.com>, Alistair Popple , Yang Shi , Nicholas Piggin , Christophe Leroy , "Aneesh Kumar K.V" , "Naveen N. Rao" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" Cc: Ryan Roberts , linux-arm-kernel@lists.infradead.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 22/25] mm: Add pte_batch_hint() to reduce scanning in folio_pte_batch() Date: Fri, 2 Feb 2024 08:07:53 +0000 Message-Id: <20240202080756.1453939-23-ryan.roberts@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240202080756.1453939-1-ryan.roberts@arm.com> References: <20240202080756.1453939-1-ryan.roberts@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240202_080942_185136_9F84364C X-CRM114-Status: GOOD ( 16.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Some architectures (e.g. arm64) can tell from looking at a pte, if some follow-on ptes also map contiguous physical memory with the same pgprot. (for arm64, these are contpte mappings). Take advantage of this knowledge to optimize folio_pte_batch() so that it can skip these ptes when scanning to create a batch. By default, if an arch does not opt-in, folio_pte_batch() returns a compile-time 1, so the changes are optimized out and the behaviour is as before. arm64 will opt-in to providing this hint in the next patch, which will greatly reduce the cost of ptep_get() when scanning a range of contptes. Tested-by: John Hubbard Signed-off-by: Ryan Roberts --- include/linux/pgtable.h | 18 ++++++++++++++++++ mm/memory.c | 20 +++++++++++++------- 2 files changed, 31 insertions(+), 7 deletions(-) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 50f32cccbd92..cba31f177d27 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -212,6 +212,24 @@ static inline int pmd_dirty(pmd_t pmd) #define arch_flush_lazy_mmu_mode() do {} while (0) #endif +#ifndef pte_batch_hint +/** + * pte_batch_hint - Number of pages that can be added to batch without scanning. + * @ptep: Page table pointer for the entry. + * @pte: Page table entry. + * + * Some architectures know that a set of contiguous ptes all map the same + * contiguous memory with the same permissions. In this case, it can provide a + * hint to aid pte batching without the core code needing to scan every pte. + * + * May be overridden by the architecture, else pte_batch_hint is always 1. + */ +static inline unsigned int pte_batch_hint(pte_t *ptep, pte_t pte) +{ + return 1; +} +#endif + #ifndef pte_advance_pfn static inline pte_t pte_advance_pfn(pte_t pte, unsigned long nr) { diff --git a/mm/memory.c b/mm/memory.c index 65fbe4f886c1..902665b27702 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -988,16 +988,21 @@ static inline int folio_pte_batch(struct folio *folio, unsigned long addr, { unsigned long folio_end_pfn = folio_pfn(folio) + folio_nr_pages(folio); const pte_t *end_ptep = start_ptep + max_nr; - pte_t expected_pte = __pte_batch_clear_ignored(pte_advance_pfn(pte, 1), flags); - pte_t *ptep = start_ptep + 1; + pte_t expected_pte = __pte_batch_clear_ignored(pte, flags); + pte_t *ptep = start_ptep; bool writable; + int nr; if (any_writable) *any_writable = false; VM_WARN_ON_FOLIO(!pte_present(pte), folio); - while (ptep != end_ptep) { + nr = pte_batch_hint(ptep, pte); + expected_pte = pte_advance_pfn(expected_pte, nr); + ptep += nr; + + while (ptep < end_ptep) { pte = ptep_get(ptep); if (any_writable) writable = !!pte_write(pte); @@ -1011,17 +1016,18 @@ static inline int folio_pte_batch(struct folio *folio, unsigned long addr, * corner cases the next PFN might fall into a different * folio. */ - if (pte_pfn(pte) == folio_end_pfn) + if (pte_pfn(pte) >= folio_end_pfn) break; if (any_writable) *any_writable |= writable; - expected_pte = pte_advance_pfn(expected_pte, 1); - ptep++; + nr = pte_batch_hint(ptep, pte); + expected_pte = pte_advance_pfn(expected_pte, nr); + ptep += nr; } - return ptep - start_ptep; + return min(ptep - start_ptep, max_nr); } /* -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel