From patchwork Fri Jul 14 00:16:40 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Elliott Mitchell X-Patchwork-Id: 13312808 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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 C6EDBC001B0 for ; Fri, 14 Jul 2023 00:22:33 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.563443.880642 (Exim 4.92) (envelope-from ) id 1qK6ZX-0007Uf-Si; Fri, 14 Jul 2023 00:22:11 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 563443.880642; Fri, 14 Jul 2023 00:22:11 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1qK6ZX-0007UY-Ov; Fri, 14 Jul 2023 00:22:11 +0000 Received: by outflank-mailman (input) for mailman id 563443; Fri, 14 Jul 2023 00:22:10 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1qK6ZW-0007US-Hb for xen-devel@lists.xenproject.org; Fri, 14 Jul 2023 00:22:10 +0000 Received: from mailhost.m5p.com (mailhost.m5p.com [74.104.188.4]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id 773b2297-21dc-11ee-8611-37d641c3527e; Fri, 14 Jul 2023 02:22:08 +0200 (CEST) Received: from m5p.com (mailhost.m5p.com [IPv6:2001:470:1f07:15ff:0:0:0:f7]) by mailhost.m5p.com (8.16.1/8.15.2) with ESMTPS id 36E0Luni098961 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Thu, 13 Jul 2023 20:22:02 -0400 (EDT) (envelope-from ehem@m5p.com) Received: (from ehem@localhost) by m5p.com (8.16.1/8.15.2/Submit) id 36E0LuEM098960; Thu, 13 Jul 2023 17:21:56 -0700 (PDT) (envelope-from ehem) 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: 773b2297-21dc-11ee-8611-37d641c3527e Message-Id: From: Elliott Mitchell To: xen-devel@lists.xenproject.org Cc: Wei Liu Cc: Anthony PERARD Date: Thu, 13 Jul 2023 17:16:40 -0700 Subject: [PATCH] docs/xen-tscmode: remove mention of numeric tsc_mode= values The better to encourage moving to setting via string mode names. Signed-off-by: Elliott Mitchell --- I'm not actually sure what tsc_mode==0 does. I didn't find other references, so I'm unsure how that should be modified. --- docs/man/xen-tscmode.7.pod | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/docs/man/xen-tscmode.7.pod b/docs/man/xen-tscmode.7.pod index 1d81a3fe18..80aea77f76 100644 --- a/docs/man/xen-tscmode.7.pod +++ b/docs/man/xen-tscmode.7.pod @@ -63,19 +63,19 @@ The non-default choices for tsc_mode are: =over 4 -=item * B (always emulate). +=item * B (always emulate). All rdtsc instructions are emulated; this is the best choice when TSC-sensitive apps are running and it is necessary to understand worst-case performance degradation for a specific hardware environment. -=item * B (never emulate). +=item * B (never emulate). This is the same as prior to Xen 4.0 and is the best choice if it is certain that all apps running in this VM are TSC-resilient and highest performance is required. -=item * B (PVRDTSCP). +=item * B (PVRDTSCP). This mode has been removed. @@ -200,10 +200,10 @@ per second per processor), this performance degradation is not noticeable OS-provided alternatives (e.g. Linux's gettimeofday). For environments where it is certain that all apps are TSC-resilient (e.g. "TSC-safeness" is not necessary) and highest performance is a -requirement, TSC emulation may be entirely disabled (tsc_mode==2). +requirement, TSC emulation may be entirely disabled (tsc_mode='native'). -The default mode (tsc_mode==0) checks TSC-safeness of the underlying -hardware on which the virtual machine is launched. If it is +The default mode (tsc_mode='always_emulate') checks TSC-safeness of the +underlying hardware on which the virtual machine is launched. If it is TSC-safe, rdtsc will execute at hardware speed; if it is not, rdtsc will be emulated. Once a virtual machine is save/restored or migrated, however, there are two possibilities: TSC remains native IF the source @@ -213,12 +213,13 @@ is emulated. Note that, though emulated, the "apparent" TSC frequency will be the TSC frequency of the initial physical machine, even after migration. -Finally, tsc_mode==1 always enables TSC emulation, regardless of +Finally, tsc_mode='always_emulate' always enables TSC emulation, regardless of the underlying physical hardware. The "apparent" TSC frequency will be the TSC frequency of the initial physical machine, even after migration. This mode is useful to measure any performance degradation that might be encountered by a tsc_mode==0 domain after migration occurs, -or a tsc_mode==3 domain when it is running on TSC-unsafe hardware. +or a tsc_mode='native_paravirt' domain when it is running on +TSC-unsafe hardware. Note that while Xen ensures that an emulated TSC is "safe" across migration, it does not ensure that it continues to tick at the same rate during