From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hanjun Guo Subject: Re: [RESEND PATCH v7 2/4] Documentation, dt, arm64/arm: dt bindings for numa. Date: Tue, 22 Dec 2015 20:54:19 +0800 Message-ID: <567947FB.2090301@linaro.org> References: <1450413433-7467-1-git-send-email-gkulkarni@caviumnetworks.com> <20151218141826.GB30229@leverpostej> <20151218180346.GF30229@leverpostej> <20151221142701.GR23092@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20151221142701.GR23092-5wv7dgnIgG8@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Will Deacon , Mark Rutland Cc: Ganapatrao Kulkarni , Ganapatrao Kulkarni , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Catalin Marinas , Grant Likely , Leif Lindholm , rfranz-YGCgFSpz5w/QT0dZR+AlfA@public.gmane.org, Ard Biesheuvel , "msalter-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , Rob Herring , Steve Capper , Al Stone , Arnd Bergmann , Pawel Moll , Ian Campbell , Kumar Gala , "Rafael J. Wysocki" , Len Brown , Marc Zyngier , Robert Richter , Prasun List-Id: devicetree@vger.kernel.org On 2015/12/21 22:27, Will Deacon wrote: > Mark, > > On Fri, Dec 18, 2015 at 06:03:47PM +0000, Mark Rutland wrote: >> On Fri, Dec 18, 2015 at 09:00:18PM +0530, Ganapatrao Kulkarni wrote: >>> Hi Mark, >>> >>> On Fri, Dec 18, 2015 at 7:48 PM, Mark Rutland wrote: >>>>> +- distance-matrix >>>>> + This property defines a matrix to describe the relative distances >>>>> + between all numa nodes. >>>>> + It is represented as a list of node pairs and their relative distance. >>>>> + >>>>> + Note: >>>>> + 1. Each entry represents distance from first node to second node. >>>>> + The distance are equal in either direction. >>>>> + 2. The distance from a node to self(local distance) is represented >>>>> + with value 10 and all inter node distance should be represented with >>>>> + value greater than 10. >>>>> + 3. distance-matrix shold have entries in lexicographical ascending >>>>> + order of nodes. >>>>> + 4. There must be only one Device node distance-map and must reside in the root node. >>>> >>>> I am still concerned that the local distance of 10 is completely >>>> arbitrary. >>> IMHO, i do not see any issue in having defined local distance to >>> arbitrary number(10). >>> inter node numa distance is relative number with respect to local distance >>> we have to fix local distance to some value, having it in dt to make >>> generic will not add >>> any additional value as compared to having the fixed local distance to 10. >> >> That's not quite true. The figure chosen for the local distance affects >> the granularity with which you can describe all distances. >> >> By using a local distance of 10 we can only encode distances in 10% >> chunks of that. Using a local distance of 100 we could encode in 1% >> chunks of that. > > Whilst I see what you're saying, the local distance of 10 seems to be > part of the ACPI spec, and is the reason why the core code defines it > that way. > > Now, we can of course do our own thing for device-tree, but I really > don't think it's worth our while to change this without a compelling > use-case. I agree, that would simplify the kernel code as well. Thanks Hanjun -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html