Messages in this thread | | | Date | Tue, 15 Feb 2011 10:38:32 +0800 | From | Gui Jianfeng <> | Subject | Re: [PATCH 5/6 v4] cfq-iosched: CFQ group hierarchical scheduling and use_hierarchy interface |
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Vivek Goyal wrote: > 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?
Ahh, I see your concern. But do we really need to show the stats even if a cgroup doesn't issue any IO on a given device? For example, on valinna kernel, when we create a new cgroup, we check the stats, say blkio.io_service_bytes, we will get "Total 0", and no disk specific stats. Currently, As soon as a cgroup issue one IO request, cfqg->blkg.dev will be updated.
Thanks, Gui
> > Thanks > Vivek > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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