Re: ftrace global trace_pipe_raw

From: Steven Rostedt
Date: Wed Jan 16 2019 - 08:47:10 EST

On Wed, 16 Jan 2019 09:00:00 +0100
Claudio <claudio.fontana@xxxxxxxxx> wrote:

> Indeed the perf event interface would be awesome, if only it would support tracing all processes.
> Unfortunately for my use case, it can only trace one process on any cpus, or all processes on one (1) cpu.
> I guess for some kind of security concerns..

Not security, but performance.

Serialized writes are best done on serialized instances (per cpu or a
single task). Having all tasks on all CPUs write to a single location
is a huge detriment to performance, and has a significant impact. Which
is why the buffer you are asking for doesn't exist.

-- Steve

> I'll take a look at how much work it would be to extend the interface for the any process/any cpu use case.
> Ciao and thank you,
> Claudio