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Date:   Thu, 1 Sep 2022 09:42:27 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Kent Overstreet <kent.overstreet@linux.dev>
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Subject: Re: [RFC PATCH 00/30] Code tagging framework and applications
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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:
> 
> > 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.