From patchwork Tue Jan 14 17:51:43 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 13939409 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 4B174E77188 for ; Tue, 14 Jan 2025 19:17:41 +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=BnnoViUsplP1otgX1eifJvfOAXuLmuFjtt6BfJTnEdQ=; b=j931filcty2TBH 8dGC/uDicf/eJpqzXE2fGX0MUnWQUYM/j+65sY7h7YyMl2QGsBLu3o5FksnDeXqRamy9W6gVXO6y3 qUWYGJbxgYjO50ya25crsr7Oka+a3l+BWS+nBqI3miOFaaCogm1izu9DQ4mxTRBbCDnarJW5uKuqe yKvdT2GWhHsL8Ia5RFlXkXSXnZbJ9Zv+Ts30bx17cnBEI6341+hqOhKBTl3HBfapj6695IOlUHAQ+ O6c0I4HOoOyptetSIYKMNDfbYi6BBuBW889hY6PZeK9Uq0v+4UCsdFwcEkMB4BEQql4eZlF1s16tz 2Z0jLgG4BPvUoPnK+oFQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tXmPv-00000009VlS-2Ezq; Tue, 14 Jan 2025 19:17:35 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tXlI0-00000009Kum-2WAd for linux-riscv@lists.infradead.org; Tue, 14 Jan 2025 18:05:21 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1736877919; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hBnzPr+bF01eZ/FcGt3b6YBzs+ceSVKdSHsMFlRMR5E=; b=ZhxlRo2FJO17mb66ETya58v8DRE0IjvguFrYxLu6s6Ff8s/Dbrb3kMCKvERBvRLjKjou3r 7dW1xpsTDKu2gZcL+gw+Uf9Rl64rgDICgN9chMFnxrCkCXh++719IaYtc/OZj7kAd2OFZh WIc0lB/xwiIkjLm65BCHxcHbMmIb5Rg= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-660-8ogZguOiNnCawOG8JxolMw-1; Tue, 14 Jan 2025 13:05:15 -0500 X-MC-Unique: 8ogZguOiNnCawOG8JxolMw-1 X-Mimecast-MFC-AGG-ID: 8ogZguOiNnCawOG8JxolMw Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id F0F9F1956050; Tue, 14 Jan 2025 18:05:11 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.39.192.55]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DFA25195608A; Tue, 14 Jan 2025 18:04:49 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org, x86@kernel.org, virtualization@lists.linux.dev, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-perf-users@vger.kernel.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, bpf@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com Cc: Juergen Gross , Ajay Kaher , Alexey Makhalov , Russell King , Catalin Marinas , Will Deacon , Huacai Chen , WANG Xuerui , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Peter Zijlstra , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , Boris Ostrovsky , Josh Poimboeuf , Pawan Gupta , Sean Christopherson , Paolo Bonzini , Andy Lutomirski , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Juri Lelli , Clark Williams , Yair Podemsky , Tomas Glozar , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Kees Cook , Andrew Morton , Christoph Hellwig , Shuah Khan , Sami Tolvanen , Miguel Ojeda , Alice Ryhl , "Mike Rapoport (Microsoft)" , Samuel Holland , Rong Xu , Nicolas Saenz Julienne , Geert Uytterhoeven , Yosry Ahmed , "Kirill A. Shutemov" , "Masami Hiramatsu (Google)" , Jinghao Jia , Luis Chamberlain , Randy Dunlap , Tiezhu Yang Subject: [PATCH v4 30/30] context-tracking: Add a Kconfig to enable IPI deferral for NO_HZ_IDLE Date: Tue, 14 Jan 2025 18:51:43 +0100 Message-ID: <20250114175143.81438-31-vschneid@redhat.com> In-Reply-To: <20250114175143.81438-1-vschneid@redhat.com> References: <20250114175143.81438-1-vschneid@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250114_100520_745225_2927B4D5 X-CRM114-Status: GOOD ( 16.17 ) X-BeenThere: linux-riscv@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-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org With NO_HZ_IDLE, we get CONTEXT_TRACKING_IDLE, so we get these transitions: ct_idle_enter() ct_kernel_exit() ct_state_inc_clear_work() ct_idle_exit() ct_kernel_enter() ct_work_flush() With just CONTEXT_TRACKING_IDLE, ct_state_inc_clear_work() is just ct_state_inc() and ct_work_flush() is a no-op. However, making them be functional as if under CONTEXT_TRACKING_WORK would allow NO_HZ_IDLE to leverage IPI deferral to keep idle CPUs idle longer. Having this enabled for NO_HZ_IDLE is a different argument than for having it for NO_HZ_FULL (power savings vs latency/performance), but the backing mechanism is identical. Add a default-no option to enable IPI deferral with NO_HZ_IDLE. Signed-off-by: Valentin Schneider --- kernel/time/Kconfig | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 7e8106a0d981f..c7398fe5382a0 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -183,9 +183,23 @@ config CONTEXT_TRACKING_USER_FORCE config CONTEXT_TRACKING_WORK bool - depends on HAVE_CONTEXT_TRACKING_WORK && CONTEXT_TRACKING_USER + depends on HAVE_CONTEXT_TRACKING_WORK && (CONTEXT_TRACKING_USER || CONTEXT_TRACKING_WORK_IDLE) default y +config CONTEXT_TRACKING_WORK_IDLE + bool + depends on HAVE_CONTEXT_TRACKING_WORK && CONTEXT_TRACKING_IDLE && !CONTEXT_TRACKING_USER + default n + help + This option enables deferral of some IPIs when they are targeted at CPUs + that are idle. This can help keep CPUs idle longer, but induces some + extra overhead to idle <-> kernel transitions and to IPI sending. + + Say Y if the power improvements are worth more to you than the added + overheads. + + Say N otherwise. + config NO_HZ bool "Old Idle dynticks config" help