On Mon, 2013-12-16 at 17:49 -0800, Andy Grover wrote: > On 12/16/2013 02:03 PM, Nicholas A. Bellinger wrote: > > On Fri, 2013-12-13 at 15:58 -0800, Andy Grover wrote: > >> Hi Nicholas, > >> > >> This patchset uses krefs to refcount structures shared across threads. > >> LIO is full of these because configfs-based configuration actions can > >> be removing an object, even while that object is being used by a SCSI > >> command. > >> > >> Using kref to free the struct on whichever thread drops the last > >> reference allows us to avoid busy-waiting in configfs removal functions. > >> Next, this set removes the statically-sized tpg lun and deve arrays in > >> favor of dynamically adding entries into rbtrees. This reduces memory > >> consumption and allows more than 255 luns per tpg and initiator mapping. > >> > >> Except for some rbtree lookups, these changes are entirely in the > >> configuration paths of Lio. I have tested these as extensively as I can, > >> and it's ready for wider testing. > >> > >> Note: patch 22 converts a percpu refcount to a normal kref. I'd argue > >> the benefit is really in the "refcount" part rather than the "percpu", > >> so a simpler kref does the job, but we might want to discuss this some > >> more. > >> > > > > It would be helpful to breakup future patches into different series > > based on: > > > > * Bugfixes > > * New features > > * Minor improvements > > Thanks for all the reviews. For the remaining changes, it'll be after > the new year before a v2. I'm still hopeful we can work out the issues > preventing the use of krefs. > So I'd like to see krefs implemented for these cases, but the rub is that configfs_group_operations->drop_items() cannot return before the last reference has dropped. > I'm somewhat surprised over the resistance to rbtrees. I guess I'll need > to hold off on resubmitting that until I have some performance data on > their effect. > I do appreciate the effort, but the extra pointer chasing here makes rbtrees prohibitively expensive for fast past operations. --nab -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
