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[34.125.73.210]) by smtp.gmail.com with ESMTPSA id q6-20020a170902a3c600b001dd0d0d26a4sm3384097plb.147.2024.04.12.11.41.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Apr 2024 11:41:15 -0700 (PDT) Date: Fri, 12 Apr 2024 11:41:11 -0700 From: David Matlack To: James Houghton Cc: Andrew Morton , Paolo Bonzini , Yu Zhao , Marc Zyngier , Oliver Upton , Sean Christopherson , Jonathan Corbet , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Shaoqin Huang , Gavin Shan , Ricardo Koller , Raghavendra Rao Ananta , Ryan Roberts , David Rientjes , Axel Rasmussen , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/7] mm/kvm: Improve parallelism for access bit harvesting Message-ID: References: <20240401232946.1837665-1-jthoughton@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240401232946.1837665-1-jthoughton@google.com> On 2024-04-01 11:29 PM, James Houghton wrote: > This patchset adds a fast path in KVM to test and clear access bits on > sptes without taking the mmu_lock. It also adds support for using a > bitmap to (1) test the access bits for many sptes in a single call to > mmu_notifier_test_young, and to (2) clear the access bits for many ptes > in a single call to mmu_notifier_clear_young. How much improvement would we get if we _just_ made test/clear_young lockless on x86 and hold the read-lock on arm64? And then how much benefit does the bitmap look-around add on top of that? 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 36E86C4345F for ; Fri, 12 Apr 2024 18:41:40 +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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=m1+/PDQZQA+bkoPapMjBo7gDwUZo1TRoRW9pP4gyPAg=; b=s5YRQu6/wSUH3A R1UPP6b7oDKqzwrFuXF/yR8o7CwCzDUyMM6FWOaomtFAI7ExZEbd3eoHBv9AHYYaYfSnTa/JmJlVA tHBHzGcmLHvOZBMPDDekBQT2JmhCqrmccLHU+WZgr+KDX0x3UioieQcnKk1jfRLXgyE/feOrO4uNs clbrpSYhF3W9hTKztVxFxIaAk6fo+niOWjRGOId/u7FZe4kshiMUD+av6sdBgERMq/He6FC+MUPYy AHOK4MojxkueXDADBMRMgO0JCpZ0KsT4aqGphqAb4qXwhYHJwzfVGrpCa6RUFCMx44d/Euth6lKbo WcH4R5eAw+CPMgsPZy4g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rvLq1-00000000ujF-0K1G; Fri, 12 Apr 2024 18:41:25 +0000 Received: from mail-pl1-x62e.google.com ([2607:f8b0:4864:20::62e]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rvLpx-00000000uhZ-2k7c for linux-arm-kernel@lists.infradead.org; Fri, 12 Apr 2024 18:41:23 +0000 Received: by mail-pl1-x62e.google.com with SMTP id d9443c01a7336-1e411e339b8so9844495ad.3 for ; Fri, 12 Apr 2024 11:41:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1712947277; x=1713552077; darn=lists.infradead.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=tE1aWPCZZJl7MoElbd+5YmoN+nAf47vnVFjNHq6stP4=; b=AChwqBHCDhgainMuosuIZTFG9XcmKAB5u+3VrErObXRkLGDSElae2szYSmE+j5YUkA uipaUiGt44Rz+Z+eh7uJOJ+ywgfPKiqhT0bhUKruq8t6PFNh7gvxkpBSCdPQBXU6bnv4 vuivLWUi48XR4iwWQPL7IkqyYfnwtkI4IWqV2wEb4ieP5hQ/QRd4VQMvC+9dzLN5IgfN icqqBs2GK/ltmdZMOg9KVMXJzHiFoM7MeQzvaU3uB3HMFowLhLWQEaVVHoxJ5bQ0J01J krpk/oDrl/1Oj9aspPaMLlq6zLl9BDlwqGebCdlYrodOYzRzHFssF4jpORGMNz4ZfcFN dEUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1712947277; x=1713552077; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=tE1aWPCZZJl7MoElbd+5YmoN+nAf47vnVFjNHq6stP4=; b=XvWajapFkQCItaBJ0N7Se7ls/38D2bms2Zr8awxUBdh4ojgJpx/kdHcVlWJxMMZULJ oOAOQlqpA7mGtCgsYpPtkFcecATc+3nxHkzQbsQh0127/7UOPOcdJgjBRt6dHMqQYX8Z MxaoEQvSj6SCNR9j0KR7GEPvS0svT4JnAJWzDq/f7lGNbOl8Slpad3vnBXATuUB2FdSe fT/bp3wjqO8QWoCGeEbocK2hQQ+BZsIedgmsLpfEk0VFQgTujpil68f6e7/Tvig+a4F6 UiAYwqkkIIvKDRR2iDITzamD0ydwcQXbQr4FHc2KaDI1Iq4Fj5xgppeMcwPT1hf+zF9c CX1A== X-Forwarded-Encrypted: i=1; AJvYcCXO/zr6kiU+WCiAieKiRGlo5IgPIxKuf2ax/kTfTaKzM3+0m82IuW6ffL5wdf1d25kn81KVvpd1m5qb4xoU1KoCv78D5aF1Ykt0csxEUUTSJeHtZiU= X-Gm-Message-State: AOJu0YwhEFiO+og8fCwAg/3PLSHf3bXG9enuNUCukra95YBg3oCKKrEF PLfItQIsSosRLsgTeBjm/WEOem5ohDC6fm9ZGGKOiEc+Q7PZ+EiuslzdzBB+ng== X-Google-Smtp-Source: AGHT+IGQO04VC0zqxkXl9HI81WqEqxeP4e4k3T6O5AVuAZB5k5Q3DvX9OiYo61rtrsCcY43kj4509A== X-Received: by 2002:a17:902:650a:b0:1e0:a1f4:95f with SMTP id b10-20020a170902650a00b001e0a1f4095fmr3460792plk.14.1712947276396; Fri, 12 Apr 2024 11:41:16 -0700 (PDT) Received: from google.com (210.73.125.34.bc.googleusercontent.com. [34.125.73.210]) by smtp.gmail.com with ESMTPSA id q6-20020a170902a3c600b001dd0d0d26a4sm3384097plb.147.2024.04.12.11.41.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Apr 2024 11:41:15 -0700 (PDT) Date: Fri, 12 Apr 2024 11:41:11 -0700 From: David Matlack To: James Houghton Cc: Andrew Morton , Paolo Bonzini , Yu Zhao , Marc Zyngier , Oliver Upton , Sean Christopherson , Jonathan Corbet , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Shaoqin Huang , Gavin Shan , Ricardo Koller , Raghavendra Rao Ananta , Ryan Roberts , David Rientjes , Axel Rasmussen , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/7] mm/kvm: Improve parallelism for access bit harvesting Message-ID: References: <20240401232946.1837665-1-jthoughton@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240401232946.1837665-1-jthoughton@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240412_114121_822459_4EC35BD0 X-CRM114-Status: GOOD ( 13.78 ) 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 On 2024-04-01 11:29 PM, James Houghton wrote: > This patchset adds a fast path in KVM to test and clear access bits on > sptes without taking the mmu_lock. It also adds support for using a > bitmap to (1) test the access bits for many sptes in a single call to > mmu_notifier_test_young, and to (2) clear the access bits for many ptes > in a single call to mmu_notifier_clear_young. How much improvement would we get if we _just_ made test/clear_young lockless on x86 and hold the read-lock on arm64? And then how much benefit does the bitmap look-around add on top of that? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel