Re: [PATCH v2] rtla/timerlat: Lock the memory of the user-space threads

[John Ogness <john.ogness@linutronix.de>]

Hi Daniel,

On 2026-11-13, Daniel Wagner <wagi@monom.org> wrote:
> diff --git a/tools/tracing/rtla/src/timerlat_u.c b/tools/tracing/rtla/src/timerlat_u.c
> index c80edaf07b00..5e7a23fb9fc3 100644
> --- a/tools/tracing/rtla/src/timerlat_u.c
> +++ b/tools/tracing/rtla/src/timerlat_u.c
> @@ -37,6 +38,13 @@ static int timerlat_u_main(int cpu, struct timerlat_u_params *params)
>  	cpu_set_t set;
>  	int retval;
>  
> +	/*
> +	 * Fault in and lock all memory before switching to a real-time
> +	 * priority, so that page faults don't show up as latency.
> +	 */

It isn't because the page faults show up as latencies. It is because
doing non-real-time work with a real-time priority is stealing the CPU
away from other real-time tasks that presumably have actual real-time
work to do.

This program peforms severeal non-real-time activities with the
real-time priority, which is not setting a good example. But I am only
reviewing your patch, not the full source.

John