From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [PATCH] x86/numa: Adjust datatypes for node and pxm Date: Mon, 23 Feb 2015 09:53:57 -0500 Message-ID: <54EB3F05.5070706@oracle.com> References: <1424542459-2615-1-git-send-email-boris.ostrovsky@oracle.com> <54EB07B10200007800062614@mail.emea.novell.com> <54EB3C61.1060606@oracle.com> <54EB4B8502000078000628B6@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <54EB4B8502000078000628B6@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: kevin.tian@intel.com, keir@xen.org, ian.campbell@citrix.com, Andrew.Cooper3@citrix.com, dario.faggioli@citrix.com, tim@xen.org, xen-devel@lists.xen.org, stefano.stabellini@citrix.com, yang.z.zhang@intel.com List-Id: xen-devel@lists.xenproject.org On 02/23/2015 09:47 AM, Jan Beulich wrote: >>>> On 23.02.15 at 15:42, wrote: >> On 02/23/2015 04:57 AM, Jan Beulich wrote: >>>>>> On 21.02.15 at 19:14, wrote: >>>> --- a/xen/arch/x86/srat.c >>>> +++ b/xen/arch/x86/srat.c >>>> @@ -21,44 +21,55 @@ >>>> #include >>>> #include >>>> >>>> +#define MAX_PXM 255 >>> Perhaps better (MAX_NUMNODES - 1) than a literal number? Or >>> even do away with it altogether, use MAX_NUMNODES - 1 in the >>> array definition and ARRAY_SIZE() elsewhere? >> I am not sure we can do this: PXMs are not guaranteed to be zero-based. >> >> And, in fact, the way we map PXMs to nodes is not quite right because of >> this --- it just so happens that PXMs are usually under 255 (and >> zero-based) and we can use them as index to 255-sized array. IIRC the >> spec defines them as 32-bit values. > Ah, yes, you're right. We may need to allocate the array dynamically > as soon as we run into a system with large PXMs. > But then we may end up with a huge and very sparse array. Maybe a hash with each element as a linked list? We will hit the first element in pretty much all cases so it should be reasonably fast. -boris