Re: [PATCH v5] tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast

[Yonghong Song <yonghong.song@linux.dev>]

On 1/9/26 11:10 AM, Alexei Starovoitov wrote:
> On Fri, Jan 9, 2026 at 6:45 AM Mathieu Desnoyers
> <mathieu.desnoyers@efficios.com> wrote:
>> On 2026-01-08 22:05, Steven Rostedt wrote:
>>> From: "Paul E. McKenney" <paulmck@kernel.org>
>> [...]
>>
>> I disagree with many elements of the proposed approach.
>>
>> On one end we have BPF wanting to hook on arbitrary tracepoints without
>> adding significant latency to PREEMPT RT kernels.
>>
>> One the other hand, we have high-speed tracers which execute very short
>> critical sections to serialize trace data into ring buffers.
>>
>> All of those users register to the tracepoint API.
>>
>> We also have to consider that migrate disable is *not* cheap at all
>> compared to preempt disable.
> Looks like your complaint comes from lack of engagement in kernel
> development.
> migrate_disable _was_ not cheap.
> Try to benchmark it now.
> It's inlined. It's a fraction of extra overhead on top of preempt_disable.
>
The following are related patches to inline migrate_disable():

35561bab768977c9e05f1f1a9bc00134c85f3e28 arch: Add the macro COMPILE_OFFSETS to all the asm-offsets.c
88a90315a99a9120cd471bf681515cc77cd7cdb8 rcu: Replace preempt.h with sched.h in include/linux/rcupdate.h
378b7708194fff77c9020392067329931c3fcc04 sched: Make migrate_{en,dis}able() inline