On Aug 1 19:22, Stephen Bates wrote: > Hi > > I am interested in exploring the impact of increased storage IO delay > on applications and was thinking of doing this by adding a delay > argument to the NVMe device model in QEMU. Is this something that > others would be interested in? If so I would be happy to work up a > patch for upstream consideration. > > If this is already do-able in QEMU I would appreciate a pointer to that. >
Hi Stephen, If this is exclusively for reads/writes, then it might better fit in the QEMU block layer. There is already the throttle filter[1] which can limit iops and bandwidth, I'm not sure if that would be a solution for you. I have not tried using it myself. You could potentially also do a simpler delay filter instead. However, the block layer filters are oblivious to the device models, so it would not work for Copy where we would end up introducing a delay on each range. In that case we would need to introduce a timer delay in QEMU. If this can be done without being too intrusive, then I think I'd be okay with adding something like that. [1]: https://github.com/qemu/qemu/blob/master/docs/throttle.txt
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