On Wed, Jan 03, 2018 at 11:32:00AM -0600, Jeremy Linton wrote: > Hi, > > On 01/03/2018 08:29 AM, Sudeep Holla wrote: > > > >On 02/01/18 02:29, Xiongfeng Wang wrote: > >>Hi, > >> > >>On 2017/12/18 20:42, Morten Rasmussen wrote: > >>>On Fri, Dec 15, 2017 at 10:36:35AM -0600, Jeremy Linton wrote: > >>>>Hi, > >>>> > >>>>On 12/13/2017 12:02 PM, Lorenzo Pieralisi wrote: > >>>>>[+Morten, Dietmar] > >>>>> > >>>>>$SUBJECT should be: > >>>>> > >>>>>arm64: topology: rename cluster_id > >>>> > >>[cut] > >>>> > >>I think we still need the information describing which cores are in one > >>cluster. Many arm64 chips have the architecture core/cluster/socket. Cores > >>in one cluster may share a same L2 cache. That information can be used to > >>build the sched_domain. If we put cores in one cluster in one sched_domain, > >>the performance will be better.(please see kernel/sched/topology.c:1197, > >>cpu_coregroup_mask() uses 'core_sibling' to build a multi-core > >>sched_domain). > > > >We get all the cache information from DT/ACPI PPTT(mainly topology) and now > >even the geometry. So ideally, the sharing information must come from that. > >Any other solution might end up in conflict if DT/PPTT and that mismatch. > > > >>So I think we still need variable to record which cores are in one > >>sched_domain for future use. > > > >I tend to say no, at-least not as is. > > > > Well, either way, with DynamiQ (and a55/a75) the cores have private L2's, > which means that the cluster sharing is happening at what is then the L3 > level. So, the code I had in earlier versions would have needed tweaks to > deal with that anyway. > Indeed. > IMHO, if we want to detect this kind of sharing for future scheduling > domains, it should probably be done independent of PPTT/DT/MIPDR by picking > out shared cache levels from struct cacheinfo *. Which makes that change > unrelated to the basic population of cacheinfo and cpu_topology in this > patchset. > Sure, that's what I meant above. i.e. we need to depend on firmware(DT/ACPI) rather than architected way(which doesn't exist anyways). Since cacheinfo abstracts DT/ACPI, it sounds right to use that to fetch any information on cache topology. -- Regards, Sudeep -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
