On 04/02/2016 07:15 PM, Nicholas A. Bellinger wrote:
On Fri, 2016-04-01 at 12:35 -0600, Chris Friesen wrote:
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.
I understand how to set up the cgroups, but don't I need to ensure that the IO
operations happen in the context of a particular cgroup? If so, how do I ensure
that the in-kernel iSCSI target traffic happens in the context of the specified
group? Are there a set of kernel threads dedicated to processing iSCSI requests?
Chris
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
