Opened 8 years ago

Closed 7 years ago

#14982 closed defect (fixed)

VBoxManage bandwidthctl breaks on low values => fixed in SVN/next maintenance

Reported by: dimaqq Owned by:
Component: virtual disk Version: VirtualBox 5.0.12
Keywords: Cc:
Guest type: other Host type: other


Setting disk bandwidth to a really low value (e.g. 1K) appears to turn off the throttle entirely, and throttle can only be re-enabled by vm power cycle (reboot is not enough).

Test: echo 3 > /proc/sys/vm/drop_caches time dd if=/dev/sdb of=/dev/null bs=1M count=10

Setup: Cloned a VM Set up IO group with 10M limit Attached existing 2nd SCSI disk to group

Test sequence: set limit to 1M booted up vm test result 1.2 MB/s repeated test (to be sure) test result 1.2 MB/s

set limit to 1K test result 91.9 MB/s

set limit to 1M test result 156 MB/s repeated test test result 82.0 MB/s

rebooted vm test result 82.0 MB/s

shut down vm started vm test resut 1.2 MB/s

Summary: It doesn't matter if low limit was set at runtime or in advance Critical value is between 210K (broken) and 225K (works) VM shutdown is needed to recover throttling

Attachments (1)

VBox.log (310.6 KB ) - added by dimaqq 8 years ago.

Download all attachments as: .zip

Change History (3)

by dimaqq, 8 years ago

Attachment: VBox.log added

comment:1 by aeichner, 7 years ago

Summary: VBoxManage bandwidthctl breaks on low valuesVBoxManage bandwidthctl breaks on low values => fixed in SVN/next maintenance

Thanks for the report, this will be fixed in the next maintenance release.

You will observe a somewhat higher throughput for really low values because VBox will process at least one I/O request from the guest per second, even if the request size is bigger than the limit to avoid stalling I/O completely.

You might also see more throughput for certain disk images because VBox limits only real reads/writes to the image, reading from an image with unallocated or compressed blocks will result in higher throughput in the guest.

comment:2 by Frank Mehnert, 7 years ago

Resolution: fixed
Status: newclosed

Fix is part of 5.1.4.

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