On 01/25/2017 12:43 AM, Sage Weil wrote: > On Wed, 25 Jan 2017, Loic Dachary wrote: >> Hi Sage, >> >> While documenting crush_reweight_bucket[1] I came accross something that >> I don't understand when reweighting uniform buckets[2]. The associated >> commit[3] is six years old but maybe your remember why the item_weight >> had to be adjusted with the average of the weight of the buckets... but >> only if there are more buckets than leaves ? > > I think it's just a half-hearted attempt to Do The Right Thing when the > situation is nonsensical. Uniform buckets are meant to be used with leave > (device) items of fixed weight (item_weight). If you (ab)use them with > bucket children, the algorithm can't really do the right thing because it > doesn't understand the child bucket weights. If there are a lot of bucket > children it resets item_weight to their average. > > This is probably pointless... we could just remove it, and perhaps warn > (or error out?) in CrushCompiler if a uniform bucket child is a > non-device. Understood. http://libcrush.org/main/libcrush/issues/8 was created to track that. Thanks ! > s > > >> >> Cheers >> >> [1] http://libcrush.org/main/libcrush/blob/wip-2-doxygen/crush/builder.h#L111 >> [2] http://libcrush.org/main/libcrush/blob/wip-2-doxygen/crush/builder.c#L1282 >> [3] http://libcrush.org/main/libcrush/commit/60f627f88c6314c5a89bb7119ead907ca8b8ef37 >> >> -- >> Loïc Dachary, Artisan Logiciel Libre >> -- Loïc Dachary, Artisan Logiciel Libre -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
