linux-kernel - Re: [PATCH 2/6] mm/swap: Introduce alternative per-cpu LRU cache locking

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Message-ID: <20210922092039.2j6efnkhmfxuzjnx@linutronix.de>
Date:   Wed, 22 Sep 2021 11:20:39 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     nsaenzju@...hat.com
Cc:     Peter Zijlstra <peterz@...radead.org>, akpm@...ux-foundation.org,
        frederic@...nel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, tglx@...utronix.de, cl@...ux.com,
        juri.lelli@...hat.com, mingo@...hat.com, mtosatti@...hat.com,
        nilal@...hat.com, mgorman@...e.de, ppandit@...hat.com,
        williams@...hat.com, anna-maria@...utronix.de,
        linux-rt-users@...r.kernel.org
Subject: Re: [PATCH 2/6] mm/swap: Introduce alternative per-cpu LRU cache
 locking

On 2021-09-22 10:47:07 [+0200], nsaenzju@...hat.com wrote:
> > *why* use migrate_disable(), that's horrible!
> 
> I was trying to be mindful of RT. They don't appreciate people taking spinlocks
> just after having disabled preemption.
> 
> I think getting local_lock(&locks->local) is my only option then. But it adds
> an extra redundant spinlock in the RT+NOHZ_FULL case.

spin_lock() does not disable preemption on PREEMPT_RT. You don't
disables preemption on purpose or did I miss that?

Sebastian