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Date: Thu, 26 Mar 2015 00:54:06 -0700
From: Peter Grehan <grehan@freebsd.org>
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To: Julian Hsiao <madoka@nyanisore.net>
Subject: Re: Several bhyve quirks
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Hi Julian,

> Thank you for your explanation and tips, Peter.  I just tried changing
> virtio-blk -> ahci-hd and preliminary results are good.  And now you've
> mentioned it, I do recall seeing slightly less performance degradation
> on guests with 2 vCPUs vs. ones with just one.

  Glad to hear that :)

>> Try using the -W option to bhyve. This will force the bhyve virtio
>> code to advertize (non-standard) MSI interrupt capability which OpenBSD
>> will then use to allocate vectors.
>
> Unfortunately -W didn't help.  This is not critical, however, and I'll
> ask around in the OpenBSD mailing list.

  I tried this out today with OpenBSD 5.7 and a CURRENT host, and it's 
actually a bug in the virtio-rnd implementation in bhyve when MSI-x 
isn't used. The early testing was with FreeBSD and Linux which both use 
MSI-x so wasn't picked up for the MSI/legacy case.

  I have a fix for CURRENT and that should make it's way into 10-stable 
shortly.

  Thanks for the report !

later,

Peter.