Hi, > > Hi All, > > > > I have got excellent results of dm-ioband, that controls the disk I/O > > bandwidth even when it accepts delayed write requests. > > > > In this time, I ran some benchmarks with a high-end storage. The > > reason was to avoid a performance bottleneck due to mechanical factors > > such as seek time. > > > > You can see the details of the benchmarks at: > > http://people.valinux.co.jp/~ryov/dm-ioband/hps/ (snip) > Secondly, why do we have to create an additional dm-ioband device for > every device we want to control using rules. This looks little odd > atleast to me. Can't we keep it in line with rest of the controllers > where task grouping takes place using cgroup and rules are specified in > cgroup itself (The way Andrea Righi does for io-throttling patches)? It isn't essential dm-band is implemented as one of the device-mappers. I've been also considering that this algorithm itself can be implemented in the block layer directly. Although, the current implementation has merits. It is flexible. - Dm-ioband can be place anywhere you like, which may be right before the I/O schedulers or may be placed on top of LVM devices. - It supports partition based bandwidth control which can work without cgroups, which is quite easy to use of. - It is independent to any I/O schedulers including ones which will be introduced in the future. I also understand it's will be hard to set up without some tools such as lvm commands. > To avoid creation of stacking another device (dm-ioband) on top of every > device we want to subject to rules, I was thinking of maintaining an > rb-tree per request queue. Requests will first go into this rb-tree upon > __make_request() and then will filter down to elevator associated with the > queue (if there is one). This will provide us the control of releasing > bio's to elevaor based on policies (proportional weight, max bandwidth > etc) and no need of stacking additional block device. I think it's a bit late to control I/O requests there, since process may be blocked in get_request_wait when the I/O load is high. Please imagine the situation that cgroups with low bandwidths are consuming most of "struct request"s while another cgroup with a high bandwidth is blocked and can't get enough "struct request"s. It means cgroups that issues lot of I/O request can win the game. > I am working on some experimental proof of concept patches. It will take > some time though. > > I was thinking of following. > > - Adopt the Andrea Righi's style of specifying rules for devices and > group the tasks using cgroups. > > - To begin with, adopt dm-ioband's approach of proportional bandwidth > controller. It makes sense to me limit the bandwidth usage only in > case of contention. If there is really a need to limit max bandwidth, > then probably we can do something to implement additional rules or > implement some policy switcher where user can decide what kind of > policies need to be implemented. > > - Get rid of dm-ioband and instead buffer requests on an rb-tree on every > request queue which is controlled by some kind of cgroup rules. > > It would be good to discuss above approach now whether it makes sense or > not. I think it is kind of fusion of io-throttling and dm-ioband patches > with additional idea of doing io-control just above elevator on the request > queue using an rb-tree. > > Thanks > Vivek > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
