Re: [PATCH] test/README: Requirements for socket buffer sizes and hardware performance events

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Aug 30, 2022 at 10:00:07PM +0200, Stefano Brivio wrote:
> Performance tests use iperf3(1) with large windows, and these sysctl
> entries are needed to run them unmodified.
> 
> The passt demo uses perf(1) to report syscall overhead, and that
> needs access to hardware performance counters for unprivileged
> users.
> 
> Reported-by: David Gibson <david(a)gibson.dropbear.id.au>
> Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>

Reviewed-by: David Gibson <david(a)gibson.dropbear.id.au>

If I get time, I'll try to add something to skip these tests if the
host sysctl isn't set appropriately.

> ---
>  test/README.md | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/test/README.md b/test/README.md
> index 581949a..72a4986 100644
> --- a/test/README.md
> +++ b/test/README.md
> @@ -47,6 +47,22 @@ Virtual machine images are built during test executions using
>  [mbuto](https://mbuto.lameexcu.se/), the shell script is sourced via _git_
>  as needed, so there's no need to actually install it.
>  
> +### Kernel parameters
> +
> +Performance tests use iperf3 with rather large TCP receiving and sending
> +windows, to decrease the likelihood of iperf3 itself becoming the bottleneck.
> +These values need to be allowed by the kernel of the host running the tests.
> +Example for /etc/sysctl.conf:
> +
> +  net.core.rmem_max = 134217728
> +  net.core.wmem_max = 134217728
> +
> +Further, the passt demo uses perf(1), relying on hardware events for performance
> +counters, to display syscall overhead. The kernel needs to allow unprivileged
> +users to access these events. Suggested entry for /etc/sysctl.conf:
> +
> +  kernel.perf_event_paranoid = -1
> +
>  ### Special requirements for continuous integration and demo modes
>  
>  Running the test suite as continuous integration or demo modes will record the

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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