On Tue, Jun 30, 2009 at 02:40:36PM +0800, Gui Jianfeng wrote: > Vivek Goyal wrote: > ... > > + > > +/* > > + * Do the accounting. Determine how much service (in terms of time slices) > > + * current queue used and adjust the start, finish time of queue and vtime > > + * of the tree accordingly. > > + * > > + * Determining the service used in terms of time is tricky in certain > > + * situations. Especially when underlying device supports command queuing > > + * and requests from multiple queues can be there at same time, then it > > + * is not clear which queue consumed how much of disk time. > > + * > > + * To mitigate this problem, cfq starts the time slice of the queue only > > + * after first request from the queue has completed. This does not work > > + * very well if we expire the queue before we wait for first and more > > + * request to finish from the queue. For seeky queues, we will expire the > > + * queue after dispatching few requests without waiting and start dispatching > > + * from next queue. > > + * > > + * Not sure how to determine the time consumed by queue in such scenarios. > > + * Currently as a crude approximation, we are charging 25% of time slice > > + * for such cases. A better mechanism is needed for accurate accounting. > > + */ > > Hi Vivek, > > The comment is out of date, would you update it accordingly? > Thanks Gui. Yes, I will update it in next posting. Vivek -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
