Re: [sig-hypervisors] [RISC-V] [tech-unixplatformspec] SBI Debug Console Extension Proposal (Draft v1)
Schwarz, Konrad <konrad.schwarz@...>
A further use case requiring fast boot
are automotive electronic control units, e.g.,
an infotainment unit.
From: sig-hypervisors@... <sig-hypervisors@...> On Behalf Of Greg Favor via lists.riscv.org
Sent: Thursday, June 2, 2022 22:50
To: Stefano Stabellini <stefano.stabellini@...>
Cc: sig-hypervisors@...; Anup Patel <apatel@...>; Heiko Stübner <heiko@...>; opensbi <opensbi@...>; tech-os-a-see@...; tech-unixplatformspec <tech-unixplatformspec@...>; Jan Remeš <jan.remes@...>
Subject: Re: [sig-hypervisors] [RISC-V] [tech-unixplatformspec] SBI Debug Console Extension Proposal (Draft v1)
On Thu, Jun 2, 2022 at 1:29 PM Stefano Stabellini <stefano.stabellini@...> wrote:
Even though we all (me included) tend to think that slowing down something like this will be inconsequential to the time to boot and/or who cares how fast or slow is boot time, in the past I have found that to be a risky presumption in certain production environments where boot time matters (especially with frequent standing up of VMs from scratch). So a worthwhile sanity check question would be 1) what percentage of early boot time is spent writing to the console with per-string SBI calls, and 2) by what order of magnitude does that percentage inflate due to SBI calls for every individual character.
Starting at 1% and inflating to 10%-100% would not be good. Starting at 0.01% and inflating to 0.1-1% is likely acceptable.
Anup, care to try and ballpark #1 and #2 above?