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Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline
- To: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
- From: David Laight <david.laight.linux@xxxxxxxxx>
- Date: Sat, 12 Sep 2026 22:14:00 +0100
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On Sat, 12 Sep 2026 11:03:34 -0700
"Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote:
> In the old kernels, yes, we have current->trc_reader_nesting++.
> In the newer kernels, Tasks Trace RCU is instead implemented in terms
> of SRCU-fast, which instead increments per-CPU counters. Which among
> other thins is a bit faster and does not need to hook into the scheduler.
Isn't that rather architecture dependant?
It is fine on x86, but on arm incrementing a per-cpu variable is
significantly expensive.
David
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