Cool ! Thanks Bart and Eric, I'll write all this up on my blog and document it (besides the mail archives). I couldn't find a single doc on lpl's anywhere.
Rafael Eric Saxe wrote: > Rafael Vanoni wrote: >> I've read a good deal of code involving lpl's but I'd like to clear a >> couple of ideas around it. If anyone could comment on these, I'd >> appreciate it. >> >> (a) lpl's are used to determine the load average of lgroups, which is >> used by the dispatcher to load balance threads around >> > Yes, that's true. An lpl actually represents an intersection between an > lgrp and a cpu partition. This subset of CPUs is what the dispatcher is > most interested in...since a thread's CPU partition (processor set) > constrains where it can run...and the dispatcher wants to consider the > lgrp's CPUs that are within that constrained set. > >> (b) each lgrp has a lpl, which in turn may have leaf lpl's for each cpu >> in that lgrp >> > There may be multiple lpls associated with an lgrp...depending on how > many cpu partitions / processor sets intersect the lgrp. The number of > lpls an lgrp can have associated is limited only by the number of > logical CPUs it contains. Leaf lgrps will have associated leaf lpls. > Just as the lpl is the result of intersecting an lgrp with a cpu > partition, the lpl hierarchy is the result of intersecting a cpu > partition with the lgrp hierarchy. > >> (c) lpl topology is created by lgrp code >> > Yes...and triggered by processor set instantiation / destruction (and by > creation of the default CPU partition, of course). > >> (d) only leaf lpl's have CPUs >> > In the implementation this is true (an artifact of the CPUs living on > the lpl via a linked list, forcing higher order lpls to track CPUs using > a composite of leaf lpls)...but conceptually this isn't true. When lpl's > are re-implemented using the processor group abstraction, this confusing > little discrepancy will go away. > >> (e) lpl's are the intersection of lgroups and CPU partitions >> > I should have read through a-e before answering the above. :) > >> I'm trying to understand where lpl's fir in the lgrp/cpus picture and >> what are their goal besides keep load averages (if any). >> > Cool. Thanks! > -Eric > _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
