From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mx.groups.io with SMTP id smtpd.web10.33277.1612184021581857185 for ; Mon, 01 Feb 2021 04:53:41 -0800 Authentication-Results: mx.groups.io; dkim=missing; spf=pass (domain: arm.com, ip: 217.140.110.172, mailfrom: vijayenthiran.subramaniam@arm.com) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4C9661476 for ; Mon, 1 Feb 2021 04:53:40 -0800 (PST) Received: from mail-yb1-f175.google.com (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 330123FA45 for ; Mon, 1 Feb 2021 04:53:40 -0800 (PST) Received: by mail-yb1-f175.google.com with SMTP id k4so16726265ybp.6 for ; Mon, 01 Feb 2021 04:53:40 -0800 (PST) X-Gm-Message-State: AOAM530+bzHovKISOak5HJyxnArb+ZgkjF++9KxxxTvt7Z8RUKi41cQq WPIvLavqUak9SNYU0YM1/0sFpPy4cBA2ReWbsKI= X-Google-Smtp-Source: ABdhPJwmP65D6fX43U4jrUJazakZ/c3RSFzhEBYqpjhSTR/RH66wCScHLCFd5LfOfX5c/F9XUq+5PEkEPS+jo/whmB8= X-Received: by 2002:a25:ce92:: with SMTP id x140mr24042487ybe.327.1612184019833; Mon, 01 Feb 2021 04:53:39 -0800 (PST) MIME-Version: 1.0 References: <1611841351-5039-1-git-send-email-vijayenthiran.subramaniam@arm.com> <1611841351-5039-3-git-send-email-vijayenthiran.subramaniam@arm.com> <165E70A6BEEFF3E5.24597@groups.io> <20210129094940.00004799@Huawei.com> <20210201111607.00007019@Huawei.com> In-Reply-To: <20210201111607.00007019@Huawei.com> From: "Vijayenthiran Subramaniam" Date: Mon, 1 Feb 2021 12:53:27 +0000 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [edk2-devel] [edk2-platforms] [PATCH v1 2/3] Platform/ARM/SgiPkg: Add HMAT ACPI table for RdN1EdgeX2 To: devel@edk2.groups.io, jonathan.cameron@huawei.com Cc: Vijayenthiran Subramanian , leif@nuviainc.com, ardb+tianocore@kernel.org, Sami Mujawar , Thomas Abraham Content-Type: text/plain; charset="UTF-8" Hi Jonathan, On Mon, Feb 1, 2021 at 11:16 AM Jonathan Cameron via groups.io wrote: > > On Fri, 29 Jan 2021 17:11:03 +0000 > Vijayenthiran Subramanian wrote: > > Hi Vijayenthiran, > > .... > > > > > > + // Memory Proximity Domain > > > > > + { > > > > > + EFI_ACPI_6_3_HMAT_STRUCTURE_MEMORY_PROXIMITY_DOMAIN_ATTRIBUTES_INIT ( > > > > > + 1, 0x0, 0x0), > > > > > + EFI_ACPI_6_3_HMAT_STRUCTURE_MEMORY_PROXIMITY_DOMAIN_ATTRIBUTES_INIT ( > > > > > + 1, 0x1, 0x1), > > > > > + }, > > > > > + > > > > > + // Latency Info > > > > > + EFI_ACPI_6_3_HMAT_STRUCTURE_SYSTEM_LOCALITY_LATENCY_AND_BANDWIDTH_INFO_INIT ( > > > > > + 0, 0, INITATOR_PROXIMITY_DOMAIN_CNT, TARGET_PROXIMITY_DOMIAIN_CNT, 100), > > > > > + { > > > > > + {0, 1}, {0, 1}, > > > > > + { > > > > > + 10, 20, > > > > > + 20, 10, > > > > > + } > > > > > + }, > > > > > > Hi, > > > > > > Now either you have a very odd machine in which latencies are round numbers that happen > > > to look like the values in SLIT or ... ? > > > > > > HMAT has very carefully defined real world units to overcome the fact that there > > > was no standard scaling etc for SLIT. It is not a good idea to put tables out > > > there which don't do this right as someone may copy this for a real system > > > and we end up with HMAT being roughly as useless for performance prediction as > > > SLIT is. That is not something I would want to see. > > > > > > Jonathan > > > > This patch is for a platform that is modelled and not for an actual board. So > > the latencies are hypothetical but ensure that the typical latency between two > > chips is represented. These tables are not expected to be copied for another > > platform without understanding what these values mean. Such a copy, without > > understanding what is being copied, would be an error in judgement on the part > > of the person doing it. The commit message of this patch (in v2) can be updated > > to exercise caution on reusing these values. > > > > [1]: https://developer.arm.com/products/system-design/fixed-virtual-platforms > > No one reads commit messages. So if you want to avoid people copying them put a > comment in the actual file. Or just make up some more plausible numbers :) > All we really need here is to avoid giving the impression that copying numbers from > SLIT is valid. > > Jonathan > Sure, I will add a comment in the file as well. Regards, Vijayenthiran