Messages in this thread | | | Date | Mon, 14 Feb 2011 13:04:29 -0500 | From | Vivek Goyal <> | Subject | Re: [PATCH 5/6 v4] cfq-iosched: CFQ group hierarchical scheduling and use_hierarchy interface |
| |
On Sat, Feb 12, 2011 at 10:21:47AM +0800, Gui Jianfeng wrote: [..] > >> +static struct cfq_group * > >> +cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create) > >> +{ > >> + struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup); > >> + struct cfq_group *cfqg = NULL; > >> + void *key = cfqd; > >> + struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info; > >> + unsigned int major, minor; > >> + > >> + cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key)); > >> + if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) { > >> + sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); > >> + cfqg->blkg.dev = MKDEV(major, minor); > >> + goto done; > >> + } > > > > Should we make this updation of this info hierarhical? > > IMHO, it's fine to defer the updation when we really get the cfqg.
But if cfqg is alrady present, we will never hit the allocation path again. So if somebody creates 2-3 level deep hierarchy and does IO only in the children cgroup, parent cgroups will potentially not get device info updated hence no visible stats?
Thanks Vivek
| |