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 ADDE8CCF9E5 for ; Mon, 27 Oct 2025 19:06:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/bfCwhk2BDRy3r/oR4WvkFD8ancMZ+pGrr34zsyRTYA=; b=gLbqg994TW4jWmrxsE4NX54iim 5pdkkvyPpMNm2I/SMaW86uCmeoWgp1toz3rGkUnfzXcuuL1ODY1GEKSaq70m+EjVLBUUm+SRzLg9p gcmSU1HUHgTW4k7O5C6qShQezuc7rndbX87fPxh5bE7heyFnNM3aASmsMlZsFS125T1/MyCojeQeJ b7L6fuNrHDi6MqzK/k53ssIUlzj1HZAEPihcRImFTg9OG7Qk3A/t/0kV9sKrQ6MF2Wnwm1ivwuW4k taCrpvx2Bf7K7MjegMPY4hXZnbGqDsMZTceEzP4ilhY805Ou+QIz3/WkrKuHf9f1LbWchvDSdRwAO Z9e4N5RA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vDSXY-0000000EcR7-1rwS; Mon, 27 Oct 2025 19:06:00 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vDSXU-0000000EcQJ-1nOX for linux-arm-kernel@lists.infradead.org; Mon, 27 Oct 2025 19:05:59 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 19FB340337; Mon, 27 Oct 2025 19:05:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 71C1CC4CEF1; Mon, 27 Oct 2025 19:05:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1761591955; bh=+dMRimA0mwlWIdgWF6jQ+Oy8xAibGJZZuh5b9HIOpW8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NUHY9px8/bWW2zpAkXA/Gs3ldmLcWdMUdWbygJgYDmS/nBl85iq0Yjc7nyNK3BeDh UazZvwa8ccPrgk0MeBOHb01ZRWbPYEIVRD4g8Z8ZhCkaQ+jQ2H9gfUI444NtA+Ood3 LnN+pIPECEwSa+kqSkY7urMWCzt16dx0EzHSqrpE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Huang Ying , Will Deacon , Anshuman Khandual , Ryan Roberts , Gavin Shan , Ard Biesheuvel , "Matthew Wilcox (Oracle)" , Yicong Yang , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Sasha Levin Subject: [PATCH 5.15 061/123] arm64, mm: avoid always making PTE dirty in pte_mkwrite() Date: Mon, 27 Oct 2025 19:35:41 +0100 Message-ID: <20251027183448.029112365@linuxfoundation.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251027183446.381986645@linuxfoundation.org> References: <20251027183446.381986645@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251027_120556_814591_F5BC4337 X-CRM114-Status: GOOD ( 17.65 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Huang Ying [ Upstream commit 143937ca51cc6ae2fccc61a1cb916abb24cd34f5 ] Current pte_mkwrite_novma() makes PTE dirty unconditionally. This may mark some pages that are never written dirty wrongly. For example, do_swap_page() may map the exclusive pages with writable and clean PTEs if the VMA is writable and the page fault is for read access. However, current pte_mkwrite_novma() implementation always dirties the PTE. This may cause unnecessary disk writing if the pages are never written before being reclaimed. So, change pte_mkwrite_novma() to clear the PTE_RDONLY bit only if the PTE_DIRTY bit is set to make it possible to make the PTE writable and clean. The current behavior was introduced in commit 73e86cb03cf2 ("arm64: Move PTE_RDONLY bit handling out of set_pte_at()"). Before that, pte_mkwrite() only sets the PTE_WRITE bit, while set_pte_at() only clears the PTE_RDONLY bit if both the PTE_WRITE and the PTE_DIRTY bits are set. To test the performance impact of the patch, on an arm64 server machine, run 16 redis-server processes on socket 1 and 16 memtier_benchmark processes on socket 0 with mostly get transactions (that is, redis-server will mostly read memory only). The memory footprint of redis-server is larger than the available memory, so swap out/in will be triggered. Test results show that the patch can avoid most swapping out because the pages are mostly clean. And the benchmark throughput improves ~23.9% in the test. Fixes: 73e86cb03cf2 ("arm64: Move PTE_RDONLY bit handling out of set_pte_at()") Signed-off-by: Huang Ying Cc: Will Deacon Cc: Anshuman Khandual Cc: Ryan Roberts Cc: Gavin Shan Cc: Ard Biesheuvel Cc: Matthew Wilcox (Oracle) Cc: Yicong Yang Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Catalin Marinas Signed-off-by: Catalin Marinas Signed-off-by: Sasha Levin --- arch/arm64/include/asm/pgtable.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index a0bfa9cd76dab..a1902dcf7a7e3 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -175,7 +175,8 @@ static inline pmd_t set_pmd_bit(pmd_t pmd, pgprot_t prot) static inline pte_t pte_mkwrite(pte_t pte) { pte = set_pte_bit(pte, __pgprot(PTE_WRITE)); - pte = clear_pte_bit(pte, __pgprot(PTE_RDONLY)); + if (pte_sw_dirty(pte)) + pte = clear_pte_bit(pte, __pgprot(PTE_RDONLY)); return pte; } -- 2.51.0