On Thu, Sep 01, 2022 at 09:05:36AM +0200, Peter Zijlstra wrote:

On Wed, Aug 31, 2022 at 11:59:41AM -0400, Kent Overstreet wrote:

quoted

Also, ftrace can drop events. Not really ideal if under system load your memory
accounting numbers start to drift.

You could attach custom handlers to tracepoints. If you were to replace
these unconditional code hooks of yours with tracepoints then you could
conditionally (say at boot) register custom handlers that do the
accounting you want.

Nobody is mandating you use the ftrace ringbuffer to consume tracepoints.
Many people these days attach eBPF scripts to them and do whatever they
want.

Look at kernel/trace/blktrace.c for a fine in-kernel !BFP example of this.