Date: Sat, 18 Mar 2023 17:29:08 +0100 From: Guido Falsi <mad@madpilot.net> To: =?UTF-8?Q?Julie_Koubov=c3=a1?= <julie@koubova.net>, freebsd-virtualization@freebsd.org Subject: Re: Bhyve process consumes way too much CPU Message-ID: <80da3a32-4c4c-5135-88b5-99419709ede9@madpilot.net> In-Reply-To: <bddc03a0-46a4-f81e-d473-afe8cc735c92@madpilot.net> References: <CABQ-j0ZH-OrZSb866iVMba-ZfxOsovGoyLd=YZ=auOiNtm-TkA@mail.gmail.com> <CABQ-j0bbTQWhM1wgYvDvvwpxQexqgtYDgN4vj8pYp2Ttu_WHHg@mail.gmail.com> <bddc03a0-46a4-f81e-d473-afe8cc735c92@madpilot.net>
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On 18/03/23 17:14, Guido Falsi wrote: > On 18/03/23 14:59, Julie Koubová wrote: >> Hey everyone, >> >> I'm running Linux (Home Assistant OS) in Bhyve on FreeBSD 13.1. I use >> PCI passthrough to allow the VM to access a USB card with a couple of >> radio dongles. The host machine is an Intel Core i3 13100 with 64 GB >> of RAM. The CPU has 4 physical cores (8 hyper-threaded). The virtual >> machine is assigned four cores. >> >> The host load averages are 0.39 0.39 0.40 right now, which seems way >> too much. The same workload was previously handled by a Raspberry Pi >> 4, and the CPU usage there was under 10% when not doing anything >> special. Inside the guest OS, the CPU usage is reported around 5%, >> which seems reasonable. > > I cannot give any definitive information, and know nothing about Home > Assistant OS but I see a problem with your reasoning here, you're > comparing CPU usage with system load, which is apples to oranges; they > are measuring two different things (albeit related to each other). > > It is quite possible to have a relatively high load with low CPU usage, > in fact I think I can see that happen when using virtual machines, since > they also have to handle their own internal interrupts and the like and > will be often ready to run, adding to the load, but actually doing very > little CPU work. > > So you should compare load to load and CPU usage to CPU usage. In > relation to a raspberry I expect load to not be significantly lower for > this kind of work, but actual CPU usage to be noticeably lower, but not > near zero. BTW, I forgot to mention that any load average less than the number of available threads means the machine is not fully loaded, so 0.50 for a 4 CPU, 8 threads machine is quite low by any measurements, while 0.50 on a machine with half the available CPUs/threads means double the actual load for that hardware. That should be accounted too. -- Guido Falsi <mad@madpilot.net>
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