Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 25 Apr 2022 21:49:28 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     "Luck, Tony" <tony.luck@intel.com>
Cc:     "hdegoede@redhat.com" <hdegoede@redhat.com>,
        "markgross@kernel.org" <markgross@kernel.org>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "bp@alien8.de" <bp@alien8.de>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "x86@kernel.org" <x86@kernel.org>, "hpa@zytor.com" <hpa@zytor.com>,
        "corbet@lwn.net" <corbet@lwn.net>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "andriy.shevchenko@linux.intel.com" 
        <andriy.shevchenko@linux.intel.com>,
        "Joseph, Jithu" <jithu.joseph@intel.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        "Williams, Dan J" <dan.j.williams@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "platform-driver-x86@vger.kernel.org" 
        <platform-driver-x86@vger.kernel.org>,
        "patches@lists.linux.dev" <patches@lists.linux.dev>,
        "Shankar, Ravi V" <ravi.v.shankar@intel.com>
Subject: Re: [PATCH v4 09/10] trace: platform/x86/intel/ifs: Add trace point
 to track Intel IFS operations
Message-ID: <20220425214928.2aac3391@gandalf.local.home>
In-Reply-To: <1752057af33e4eb28bcea0fd75e44048@intel.com>
References: <20220419163859.2228874-1-tony.luck@intel.com>
        <20220422200219.2843823-1-tony.luck@intel.com>
        <20220422200219.2843823-10-tony.luck@intel.com>
        <20220425105251.3f5e8021@gandalf.local.home>
        <1752057af33e4eb28bcea0fd75e44048@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Mon, 25 Apr 2022 16:49:35 +0000
"Luck, Tony" <tony.luck@intel.com> wrote:

> I see two paths:
> 
> 1) Create a new user friendly trace point for each new scan mode.
> 2) Just provide a generic one that dumps both the 64-bit WRMSR and RDMSR values.
> 
> Q: Are trace points "expensive" in some way ... so better to just have one than three?
>      Or are the cheap enough that decoding for the user is an OK thing?

Yes, they are expensive as each TRACE_EVENT() can add a few KB of text and
data. But you can add a DECLARE_EVENT_CLASS() and then add "printk"
differences that are less memory heavy.

See DEFINE_EVENT_PRINT().

-- Steve