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

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Message-ID: <CAM9d7cguuyY74L9XK=z384bwO6nTCw4XOFNK1yaJhhmKYTBBoA@mail.gmail.com>
Date:   Tue, 1 Mar 2022 10:03:57 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Peter Zijlstra <peterz@...radead.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 <bpf@...r.kernel.org>, Radoslaw Burny <rburny@...gle.com>
Subject: Re: [PATCH 2/4] locking: Apply contention tracepoints in the slow path

Hi Peter,

On Tue, Mar 1, 2022 at 12:44 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> 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.

I can move it into the slow path with caller ip.

Thanks,
Namhyung