From nobody Mon Feb 9 17:21:58 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass(p=quarantine dis=none) header.from=suse.com ARC-Seal: i=1; a=rsa-sha256; t=1617270884; cv=none; d=zohomail.com; s=zohoarc; b=UvIJ9oAkcSnRdqMPIKoSyJWNQLZXUCyCHsVxvJH/JSALSfHtpZSdGssOJiUYgLdD2OSjzZy99sNS2jSlug7AUD80Td7pU46JUA8VQQ8m9DR7BcIh5OeTf0/vHkTTqBseQohZbFHi9Q+A9S2vrMIq7fy5MmdGckeWWiEHfWOKxs0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1617270884; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=QdS547I0MHs8GHpeGea/kzNdcUxE2McJtcRJ1hPnylM=; b=TUmtZ552LCpiluOusZdOhQ2hZ7muugztsxKVoTBd8gioHY5dbmy2RSQOgOLbci8iMwJ578cWDXiKeCYSzsXmOlC8fkUzdri3CPMiC8esMtu0P1qSlG5m9yENPzw3mZffxcETOmcwWWH8jOwP+whtgrtT1TfQe9BpwsHRGOQhYCY= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass header.from= (p=quarantine dis=none) header.from= Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1617270884760748.9043936580016; Thu, 1 Apr 2021 02:54:44 -0700 (PDT) Received: from list by lists.xenproject.org with outflank-mailman.104263.199218 (Exim 4.92) (envelope-from ) id 1lRu23-0006Vh-3B; Thu, 01 Apr 2021 09:54:31 +0000 Received: by outflank-mailman (output) from mailman id 104263.199218; Thu, 01 Apr 2021 09:54:31 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lRu23-0006Va-05; Thu, 01 Apr 2021 09:54:31 +0000 Received: by outflank-mailman (input) for mailman id 104263; Thu, 01 Apr 2021 09:54:29 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lRu21-0006VT-IZ for xen-devel@lists.xenproject.org; Thu, 01 Apr 2021 09:54:29 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 162e1716-1d1c-432e-86aa-435eef0c2cd3; Thu, 01 Apr 2021 09:54:28 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 262E0B032; Thu, 1 Apr 2021 09:54:28 +0000 (UTC) X-Outflank-Mailman: Message body and most headers restored to incoming version X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 162e1716-1d1c-432e-86aa-435eef0c2cd3 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1617270868; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QdS547I0MHs8GHpeGea/kzNdcUxE2McJtcRJ1hPnylM=; b=Yw2aNBfYvGgfmOIZZAydVv7NE5hING06Tbr1dHmF+WBYBdMmxtdW4AzLiCWY3VRhuyLZzc AZcIoARXZo0GVFdu7M7vh+nGvIdi9FjUUtTruyszBKAdP8hw88mvwJ6fS9zcFqMXoJgSoe Uj3Isdgek2k9ntlCRjq6CB31hRlAAnI= Subject: [PATCH v4 2/3] x86/time: yield to hyperthreads after updating TSC during rendezvous From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: Message-ID: <81da85eb-2e8e-9b76-2fb3-2beddc33e9af@suse.com> Date: Thu, 1 Apr 2021 11:54:27 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @suse.com) Content-Type: text/plain; charset="utf-8" Since we'd like the updates to be done as synchronously as possible, make an attempt at yielding immediately after the TSC write. Signed-off-by: Jan Beulich Reviewed-by: Roger Pau Monn=C3=A9 --- v4: New. --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -1708,7 +1708,14 @@ static void time_calibration_tsc_rendezv atomic_inc(&r->semaphore); =20 if ( i =3D=3D 0 ) + { write_tsc(master_tsc); + /* + * Try to give our hyperthread(s), if any, a chance to do + * the same as instantly as possible. + */ + cpu_relax(); + } =20 while ( atomic_read(&r->semaphore) !=3D (2*total_cpus - 1) ) cpu_relax(); @@ -1730,7 +1737,14 @@ static void time_calibration_tsc_rendezv } =20 if ( i =3D=3D 0 ) + { write_tsc(master_tsc); + /* + * Try to give our hyperthread(s), if any, a chance to do + * the same as instantly as possible. + */ + cpu_relax(); + } =20 atomic_inc(&r->semaphore); while ( atomic_read(&r->semaphore) > total_cpus )