From: Peter Zijlstra <peterz@infradead.org>
To: Vineeth Remanan Pillai <vineeth@bitbyteword.org>
Cc: "Steven Rostedt" <rostedt@goodmis.org>,
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Subject: Re: [PATCH 01/15] tracepoint: Add trace_invoke_##name() API
Date: Thu, 12 Mar 2026 16:53:26 +0100 [thread overview]
Message-ID: <20260312155326.GB1282955@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <CAO7JXPhg-Etspj9YahZrq8cmZ2K6AGWDrMnHO+oD96P_SmOLBw@mail.gmail.com>
On Thu, Mar 12, 2026 at 11:39:06AM -0400, Vineeth Remanan Pillai wrote:
> On Thu, Mar 12, 2026 at 11:13 AM Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > On Thu, 12 Mar 2026 11:04:56 -0400
> > "Vineeth Pillai (Google)" <vineeth@bitbyteword.org> wrote:
> >
> > > Add trace_invoke_##name() as a companion to trace_##name(). When a
> > > caller already guards a tracepoint with an explicit enabled check:
> > >
> > > if (trace_foo_enabled() && cond)
> > > trace_foo(args);
> > >
> > > trace_foo() internally repeats the static_branch_unlikely() test, which
> > > the compiler cannot fold since static branches are patched binary
> > > instructions. This results in two static-branch evaluations for every
> > > guarded call site.
> > >
> > > trace_invoke_##name() calls __do_trace_##name() directly, skipping the
> > > redundant static-branch re-check. This avoids leaking the internal
> > > __do_trace_##name() symbol into call sites while still eliminating the
> > > double evaluation:
> > >
> > > if (trace_foo_enabled() && cond)
> > > trace_invoke_foo(args); /* calls __do_trace_foo() directly */
> > >
> > > Three locations are updated:
> > > - __DECLARE_TRACE: invoke form omits static_branch_unlikely, retains
> > > the LOCKDEP RCU-watching assertion.
> > > - __DECLARE_TRACE_SYSCALL: same, plus retains might_fault().
> > > - !TRACEPOINTS_ENABLED stub: empty no-op so callers compile cleanly
> > > when tracepoints are compiled out.
> > >
> > > Suggested-by: Steven Rostedt <rostedt@goodmis.org>
> > > Suggested-by: Peter Zijlstra <peterz@infradead.org>
> > > Signed-off-by: Vineeth Pillai (Google) <vineeth@bitbyteword.org>
> > > Assisted-by: Claude:claude-sonnet-4-6
> >
> > I'm guessing Claude helped with the other patches. Did it really help with this one?
> >
>
> Claude wrote and build tested the whole series based on my guidance
> and prompt :-). I verified the series before sending it out, but
> claude did the initial work.
That seems like an unreasonable waste of energy. You could've had claude
write a Coccinelle script for you and saved a ton of tokens.
next prev parent reply other threads:[~2026-03-12 15:53 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-12 15:04 [PATCH 00/15] tracepoint: Avoid double static_branch evaluation at guarded call sites Vineeth Pillai (Google)
2026-03-12 15:04 ` [PATCH 01/15] tracepoint: Add trace_invoke_##name() API Vineeth Pillai (Google)
2026-03-12 15:12 ` Steven Rostedt
2026-03-12 15:39 ` Vineeth Remanan Pillai
2026-03-12 15:53 ` Peter Zijlstra [this message]
2026-03-12 16:05 ` Vineeth Remanan Pillai
2026-03-14 0:24 ` Keith Busch
2026-03-12 15:04 ` [PATCH 03/15] io_uring: Use trace_invoke_##name() at guarded tracepoint call sites Vineeth Pillai (Google)
2026-03-12 15:24 ` Keith Busch
2026-03-12 15:38 ` Steven Rostedt
2026-03-12 15:12 ` [PATCH 00/15] tracepoint: Avoid double static_branch evaluation at guarded " Mathieu Desnoyers
2026-03-12 15:23 ` Steven Rostedt
2026-03-12 15:28 ` Mathieu Desnoyers
2026-03-12 15:40 ` Steven Rostedt
2026-03-12 15:49 ` Mathieu Desnoyers
2026-03-12 15:54 ` Peter Zijlstra
2026-03-12 15:57 ` Mathieu Desnoyers
2026-03-12 16:08 ` Vineeth Remanan Pillai
2026-03-12 16:54 ` Andrii Nakryiko
2026-03-12 17:02 ` Steven Rostedt
2026-03-13 14:02 ` Vineeth Remanan Pillai
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