linux-kernel - Re: [PATCH V6 0/7] ACPI: Support Generic Initiator proximity domains

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Message-ID: <20200103130850.00000ace@Huawei.com>
Date:   Fri, 3 Jan 2020 13:08:50 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Brice Goglin <brice.goglin@...il.com>
CC:     <linux-mm@...ck.org>, <linux-acpi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <x86@...nel.org>,
        Keith Busch <kbusch@...nel.org>, <jglisse@...hat.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>, <linuxarm@...wei.com>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Tao Xu <tao3.xu@...el.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH V6 0/7] ACPI: Support Generic Initiator proximity
 domains

On Fri, 3 Jan 2020 13:18:59 +0100
Brice Goglin <brice.goglin@...il.com> wrote:

> Le 03/01/2020 à 11:09, Jonathan Cameron a écrit :
> >
> > 1) If the memory and processor are in the same domain, that should mean the
> > access characteristics within that domain are the best in the system.
> > It is possible to have a setup with very low latency access
> > from a particular processor but also low bandwidth.  Another domain may have
> > high bandwidth but long latency.   Such systems may occur, but they are probably
> > going to not be for 'normal memory the OS can just use'.
> >
> > 2) If we have a relevant "Memory Proximity Domain Attributes Structure"
> > Note this was renamed in acpi 6.3 from "Address Range Structure" as
> > it no longer has any address ranges.
> > (which are entirely optional btw) that indicates that the memory controller
> > for a given memory lies in the proximity domain of the Initiator specified.
> > If that happens we ignore cases where hmat says somewhere else is nearer
> > via bandwidth and latency.
> >
> > For case 1) I'm not sure we actually enforce it.
> > I think you've hit case 2).  
> >
> > Removing the address range structures should work, or as you say you can
> > move that memory into separate memory nodes.  
> 
> 
> I removed the "processor proximity domain valid" flag from the address
> range structure of node2, and the GI is now its access0 initiator
> instead of node2 itself. Looks like it confirms I was in case 2)
> 
> Thanks
> 
> Brice

Cool. I was wondering if that change would work fine.
It is a somewhat crazy setup so I didn't have an equivalent in my test set.

Sounds like all is working as expected.

Thanks,

Jonathan