The xlist has means of efficiently removing entries from a list. I think you'll find those in the path where we start tearing down a PG, and membership on this list is a bit different from membership in the ShardedThreadPool. It's all about the particulars of each design, and I don't have that in my head — you'd need to examine it. -Greg On Tue, Nov 10, 2015 at 4:20 PM, 池信泽 <xmdxcxz@xxxxxxxxx> wrote: > I wonder if we want to keep the PG from going out of scope at an > inopportune time, why snap_trim_queue and scrub_queue declared as > xlist<PG*> instead of xlist<PGRef>? > > 2015-11-11 2:28 GMT+08:00 Gregory Farnum <gfarnum@xxxxxxxxxx>: >> On Tue, Nov 10, 2015 at 7:19 AM, 池信泽 <xmdxcxz@xxxxxxxxx> wrote: >>> hi, all: >>> >>> op_wq is declared as ShardedThreadPool::ShardedWQ < pair <PGRef, >>> OpRequestRef> > &op_wq. I do not know why we should use PGRef in this? >>> >>> Because the overhead of the smart pointer is not small. Maybe the >>> raw point PG* is also OK? >>> >>> If op_wq is changed to ShardedThreadPool::ShardedWQ < pair <PG*, >>> OpRequestRef> > &op_wq (using raw point) >>> >>> the latency for PrioritizedQueue:;enqueue decrease from 3.38us -> 1.89us >>> >>> the latency for PrioritizedQueue:;dequeue decrease from 3.44us -> 1.65us >>> >>> Is this make sense to you? >> >> In general we use PGRefs rather than PG pointers. I think we actually >> rely on the references here to keep the PG from going out of scope at >> an inopportune time, but if it halves the cost of queuing actions it >> might be worth the effort of avoiding that. >> -Greg > > > > -- > Regards, > xinze -- 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
