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 X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2EF8C7618F for ; Fri, 19 Jul 2019 00:59:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC1412184E for ; Fri, 19 Jul 2019 00:59:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726769AbfGSA7Z (ORCPT ); Thu, 18 Jul 2019 20:59:25 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:34022 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726539AbfGSA7H (ORCPT ); Thu, 18 Jul 2019 20:59:07 -0400 Received: by mail-pf1-f193.google.com with SMTP id b13so13392514pfo.1 for ; Thu, 18 Jul 2019 17:59:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=MlOkGjlKe23/Wup3KXevKcIurY4O1G8mMmCmtgnZfrQ=; b=HOhKSzYqV6KqMIm52mdYN9BLgbiOqdSSCp2b9Ly/J/gPatb5FqP+ZgppPgI0Bff+xr OR2CQNyClTIQ/AtXimOwzy5tVNmbVqkPf81b8B25eX+b9l2fvRPSMN3pn1Y07E50F5ux aeLhBX3k8V5k3N6u8bP6It6sjSDjCewNi80MCRLeayUqVtig4nQgqZ6nF01jfgKHf711 OtuoDqqT2nkmeDtaCoLDnDeym+xUH2PFQvAHXWWef6sLJn1vOrmSAKEDjTZxSod98yNI znZSNavSAFAH1xtr3gTDNVFI3CE3hJAS4Xs9tcOBwyfhq9QLWP90YMVTC3K4u9Dy3O9B PpnQ== X-Gm-Message-State: APjAAAUnE3aIFZT/i6r0tzwhnJkn1a0DPhI+TcUDyUeImhtHvJHgfhQY Y0cVBVM2JYt7N1BIvH1rXdxAyzJV/3o= X-Google-Smtp-Source: APXvYqzTrtPwuTC0VDUpV7kyMgndF0s9Wa/i8EXJD31LgPjv9Tl6Ni8zmXCml5tRSEyXiz6OMjd2eQ== X-Received: by 2002:a17:90a:8a15:: with SMTP id w21mr54640132pjn.134.1563497946884; Thu, 18 Jul 2019 17:59:06 -0700 (PDT) Received: from htb-2n-eng-dhcp405.eng.vmware.com ([66.170.99.1]) by smtp.gmail.com with ESMTPSA id j128sm14025166pfg.28.2019.07.18.17.59.05 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 18 Jul 2019 17:59:06 -0700 (PDT) From: Nadav Amit To: Andy Lutomirski , Dave Hansen Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Nadav Amit , Dave Hansen Subject: [PATCH v3 6/9] x86/mm/tlb: Do not make is_lazy dirty for no reason Date: Thu, 18 Jul 2019 17:58:34 -0700 Message-Id: <20190719005837.4150-7-namit@vmware.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190719005837.4150-1-namit@vmware.com> References: <20190719005837.4150-1-namit@vmware.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Blindly writing to is_lazy for no reason, when the written value is identical to the old value, makes the cacheline dirty for no reason. Avoid making such writes to prevent cache coherency traffic for no reason. Cc: Andy Lutomirski Cc: Peter Zijlstra Suggested-by: Dave Hansen Signed-off-by: Nadav Amit --- arch/x86/mm/tlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index af80c274c88d..89f83ad19507 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -322,7 +322,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, __flush_tlb_all(); } #endif - this_cpu_write(cpu_tlbstate_shared.is_lazy, false); + if (was_lazy) + this_cpu_write(cpu_tlbstate_shared.is_lazy, false); /* * The membarrier system call requires a full memory barrier and -- 2.20.1