linux-kernel - Re: [PATCH 2/4] locking: Apply contention tracepoints in the slow path

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Message-ID: <Yh3cwBloddIGvCjU@hirez.programming.kicks-ass.net>
Date:   Tue, 1 Mar 2022 09:43:44 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Byungchul Park <byungchul.park@....com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
        bpf@...r.kernel.org, Radoslaw Burny <rburny@...gle.com>
Subject: Re: [PATCH 2/4] locking: Apply contention tracepoints in the slow
 path

On Mon, Feb 28, 2022 at 05:04:10PM -0800, Namhyung Kim wrote:
> @@ -80,7 +81,9 @@ static inline void queued_read_lock(struct qrwlock *lock)
>  		return;
>  
>  	/* The slowpath will decrement the reader count, if necessary. */
> +	LOCK_CONTENTION_BEGIN(lock, LCB_F_READ);
>  	queued_read_lock_slowpath(lock);
> +	LOCK_CONTENTION_END(lock);
>  }
>  
>  /**
> @@ -94,7 +97,9 @@ static inline void queued_write_lock(struct qrwlock *lock)
>  	if (likely(atomic_try_cmpxchg_acquire(&lock->cnts, &cnts, _QW_LOCKED)))
>  		return;
>  
> +	LOCK_CONTENTION_BEGIN(lock, LCB_F_WRITE);
>  	queued_write_lock_slowpath(lock);
> +	LOCK_CONTENTION_END(lock);
>  }

> @@ -82,7 +83,9 @@ static __always_inline void queued_spin_lock(struct qspinlock *lock)
>  	if (likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL)))
>  		return;
>  
> +	LOCK_CONTENTION_BEGIN(lock, 0);
>  	queued_spin_lock_slowpath(lock, val);
> +	LOCK_CONTENTION_END(lock);
>  }

Can you please stick that _inside_ the slowpath? You really don't want
to inline that.