On Fri, 2016-04-01 at 12:35 -0600, Chris Friesen wrote:
> On 03/31/2016 01:05 AM, Nicholas A. Bellinger wrote:
> > On Wed, 2016-03-16 at 10:48 -0600, Chris Friesen wrote:
> >> On 03/11/2016 01:45 AM, Nicholas A. Bellinger wrote:
> >>> On Thu, 2016-03-10 at 23:30 -0800, Christoph Hellwig wrote:
> >>>> On Thu, Mar 10, 2016 at 04:24:25PM -0600, Chris Friesen wrote:
> >>>>> Hi,
> >>>>>
> >>>>> I'm looking for information on whether the iSCSI target in the kernel offers
> >>>>> any way to do QoS between traffic driven by different initiators.
> >>>>>
> >>>>> I'm trying to make sure that one initiator can't do a denial-of-service
> >>>>> attack against others.
> >>>>>
> >>>>> Does the kernel target have this sort of thing built-in, or do I need to
> >>>>> look at network traffic-shaping to achieve this?
> >>>>
> >>>> It doesn't right now, but it shouldn't be hard to integrate it with
> >>>> blk cgroups.
> >>>
> >>> For iscsi-target application QoS, the per session command sequence
> >>> number window depth (CmdSN) exists to enforce per InitiatorName limits
> >>> via TPG default_cmdsn_depth + se_node_acl->queue_depth configfs
> >>> attributes.
> >>>
> >>> Note these values can be changed on the fly for iscsi-target using
> >>> explicit se_node_acl->acl_group, but currently require a se_session
> >>> reinstatement event for updated ExpCmdSN + MaxCmdSN to take effect.
> >>
> >> On a slightly different note, is there any way to throttle or limit the overall
> >> bandwidth consumed by the iSCSI target in the kernel? I'd like to ensure that
> >> the iSCSI traffic doesn't completely swamp the host accesses to the same block
> >> device.
> >>
> >> I suppose I could do networking-based traffic shaping, but are there any
> >> controls in the block IO subsystem?
> >>
> >
> > On a individual block_device backend basis, block cgroups is the
> > preferred method for doing this.
> >
> > Note that any rate limiting imposed by block cgroups is subject to the
> > current se_node_acl->queue_depth enforced across all LUNs within a given
> > iscsi session.
>
>
> How would I use cgroups with the kernel iSCSI target? Is there a set of kernel
> threads dedicated to the iSCSI target that I can assign to a particular group?
>
block cgroups can set I/O throttling (bandwidth + IOPs) limits for any
normal struct block_device.
These values are configured via blkio.throttle.* resource class, and the
limits are imposed independently of the block_device's association with
target_core_mod backend driver export. Namely:
blkio.throttle.write_iops_device
blkio.throttle.read_iops_device
blkio.throttle.write_bps_device
blkio.throttle.read_bdp_device
Some examples using these values, plus more blkio.* info is here:
http://events.linuxfoundation.org/sites/events/files/slides/cgroups_0.pdf.
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