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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Clark Williams <clark.williams@gmail.com>
Cc: bigeasy@linutronix.com, tglx@linutronix.com,
	linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PREEMPT_RT PATCH 2/3] i915: convert all irq_locks spinlocks to raw spinlocks
Date: Tue, 3 Sep 2019 15:09:30 +0200
Message-ID: <20190903130930.isctetjvzckgubuh@linutronix.de> (raw)
In-Reply-To: <20190903080335.pe45dmgmjvdvbyd4@linutronix.de>

On 2019-09-03 10:03:35 [+0200], To Clark Williams wrote:
> anything in a brief test. What I saw however is that switching to
> fullscreen while playing a video gives me ~0.5 to ~2ms latency. This is
> has nothing to do with this change, I have to dig deeper… It might be
> one of the preempt_disable() section I just noticed.
> I would prefer to keep the lock non-raw unless there is actual need for
> it.

That latency spike is caused by the iommu, qi_submit_sync() to be exact.
Without the iomm I don't see much difference between the two patches…
 
Sebastian

  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-20  0:33 [PREEMPT_RT PATCH 0/3] i915 fixups for lockdep/lockdebugging Clark Williams
2019-08-20  0:33 ` [PREEMPT_RT PATCH 1/3] i915: do not call lockdep_assert_irqs_disabled() on PREEMPT_RT Clark Williams
2019-09-25 16:47   ` Sebastian Andrzej Siewior
2019-08-20  0:33 ` [PREEMPT_RT PATCH 2/3] i915: convert all irq_locks spinlocks to raw spinlocks Clark Williams
2019-09-03  8:03   ` Sebastian Andrzej Siewior
2019-09-03 13:09     ` Sebastian Andrzej Siewior [this message]
2019-09-16 21:21     ` Sean V Kelley
2019-09-27 12:29       ` Sebastian Andrzej Siewior
     [not found]         ` <CAPAFJkofsYgSOxzM4JDkOV3Ra0C-AEpU2eZJjR9F9e_qv-6=rg@mail.gmail.com>
2019-09-27 15:18           ` Sean V Kelley
2019-08-20  0:33 ` [PREEMPT_RT PATCH 3/3] i915: convert uncore lock to raw spinlock Clark Williams

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