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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 240A0C48260 for ; Tue, 13 Feb 2024 16:55:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ADC5C8D0016; Tue, 13 Feb 2024 11:55:00 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A66098D000E; Tue, 13 Feb 2024 11:55:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 906418D0016; Tue, 13 Feb 2024 11:55:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 7D67E8D000E for ; Tue, 13 Feb 2024 11:55:00 -0500 (EST) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 25FFA160352 for ; Tue, 13 Feb 2024 16:55:00 +0000 (UTC) X-FDA: 81787380360.26.9A81893 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf07.hostedemail.com (Postfix) with ESMTP id 85C974001B for ; Tue, 13 Feb 2024 16:54:58 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=none; spf=pass (imf07.hostedemail.com: domain of mark.rutland@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=mark.rutland@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707843298; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=CMri00MoKhSqJ8uAcIfrMINrdTHiogXtd3Ypy52vvSs=; b=KbpeGAq0OgtJta2XuNWpfcyEEhdsib+RLMi7/3xDS9mfMIsiFfRKLMtNHW8981QZ272xdT wApSrxVl0swuEpywgnh9KDCqRGFIIYivZXDezotggTUeTINr7ACrsuoG4Yko6IPzfAx6Xp +cAzrLJb5mrkzZ6oNC+kxBqoUboMl7o= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1707843298; a=rsa-sha256; cv=none; b=MVIQtGV2Uoy/J4RU4OL6pDD34efUD78NRH4/oS/zfDNd0HCLzIwQOcdBnEEgYuqYgfq7nb FxH9amHwhuVYQ9WfbF0tNyxJ8bPrd+qFDcoOdND298Ot6dooGW7kmjdM6F+NSC7fdGue8U iypn2DS9S/GlUshhwwRJO1wlz6N1fFE= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=none; spf=pass (imf07.hostedemail.com: domain of mark.rutland@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=mark.rutland@arm.com; dmarc=pass (policy=none) header.from=arm.com 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 E5C0DDA7; Tue, 13 Feb 2024 08:55:38 -0800 (PST) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.36.130]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DE5853F5A1; Tue, 13 Feb 2024 08:54:53 -0800 (PST) Date: Tue, 13 Feb 2024 16:54:51 +0000 From: Mark Rutland To: Ryan Roberts Cc: Catalin Marinas , Will Deacon , Ard Biesheuvel , Marc Zyngier , James Morse , Andrey Ryabinin , Andrew Morton , Matthew Wilcox , 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. 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Peter Anvin" , linux-arm-kernel@lists.infradead.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 23/25] arm64/mm: Implement pte_batch_hint() Message-ID: References: <20240202080756.1453939-1-ryan.roberts@arm.com> <20240202080756.1453939-24-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240202080756.1453939-24-ryan.roberts@arm.com> X-Stat-Signature: hqaj4idx7qpwb9ximsepxyjtr76s64bu X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 85C974001B X-Rspam-User: X-HE-Tag: 1707843298-994560 X-HE-Meta: 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 BvQRg9Ng wWRiyGf3cUxPnApX3M8PFk0XjahSEvb1yV9GZhyKRyur6FC/tY/vcVtWlOtWcqavHlUpIZFKSTDvoOyQ1zSPZusczrsK6L/F3zjPRCGyIyhQDQ08dkDGaoPWIgLdQEyFs7ILmRXQsgRdk602yj8FCX/+12dSpHm2bzRYhFs1hy5Nc0+8MBrXz4HaPhd6vzRaDhQzWoiXaz8ylhSCoy1Hq4v+eIPEcHRLnNnX0IaFNjbw20IpTJMS4Gt668rHSzePqJn6/IjWFMHuRqJuUeqsVglfIZzNqyHZifWyXhHq1Dr8lUw51LiB6uoUslybkrkNuCcxqV/r/vsXa4j17VpPeevGrx0tN+TvnpUyDAc04kfQ4mCfJxRTqfLHJ8LoZaNFa6Bi4qE6eYPYqMXH3VU1IE2Egpw== 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: List-Subscribe: List-Unsubscribe: On Fri, Feb 02, 2024 at 08:07:54AM +0000, Ryan Roberts wrote: > When core code iterates over a range of ptes and calls ptep_get() for > each of them, if the range happens to cover contpte mappings, the number > of pte reads becomes amplified by a factor of the number of PTEs in a > contpte block. This is because for each call to ptep_get(), the > implementation must read all of the ptes in the contpte block to which > it belongs to gather the access and dirty bits. > > This causes a hotspot for fork(), as well as operations that unmap > memory such as munmap(), exit and madvise(MADV_DONTNEED). Fortunately we > can fix this by implementing pte_batch_hint() which allows their > iterators to skip getting the contpte tail ptes when gathering the batch > of ptes to operate on. This results in the number of PTE reads returning > to 1 per pte. > > Tested-by: John Hubbard > Signed-off-by: Ryan Roberts Acked-by: Mark Rutland Mark. > --- > arch/arm64/include/asm/pgtable.h | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index ad04adb7b87f..353ea67b5d75 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -1220,6 +1220,15 @@ static inline void contpte_try_unfold(struct mm_struct *mm, unsigned long addr, > __contpte_try_unfold(mm, addr, ptep, pte); > } > > +#define pte_batch_hint pte_batch_hint > +static inline unsigned int pte_batch_hint(pte_t *ptep, pte_t pte) > +{ > + if (!pte_valid_cont(pte)) > + return 1; > + > + return CONT_PTES - (((unsigned long)ptep >> 3) & (CONT_PTES - 1)); > +} > + > /* > * The below functions constitute the public API that arm64 presents to the > * core-mm to manipulate PTE entries within their page tables (or at least this > -- > 2.25.1 >