From: Catalin Marinas <catalin.marinas@arm.com>
To: James Clark <james.clark@arm.com>
Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
suzuki.poulose@arm.com, mathieu.poirier@linaro.org,
mike.leach@linaro.org, leo.yan@linaro.org, broonie@kernel.org,
linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH 0/1] arm64: defconfig: Add Coresight as module
Date: Thu, 22 Sep 2022 11:52:48 +0100 [thread overview]
Message-ID: <Yyw+gHXLG/fXoQbT@arm.com> (raw)
In-Reply-To: <adc70f4a-83f8-2bcc-87f1-28db004ae8e8@arm.com>
On Thu, Sep 22, 2022 at 10:34:45AM +0100, James Clark wrote:
> On 21/09/2022 16:08, Catalin Marinas wrote:
> > 2. Always on CONFIG_PID_IN_CONTEXTIDR (we might as well remove the
> > Kconfig entry). This would write the root pid namespace value
> > (task_pid_nr()).
>
> If we're not worried about the overhead after all, this would be the
> easiest solution. And then SPE or Coresight already decide whether they
> want to use the value or not, so no further changes are needed.
>
> From Leo's patch there is a table that shows a 1% overhead with it
> enabled permanently, and I've heard a figure like that mentioned before.
> So I could also resurrect that patch to use static keys? Although it's a
> bit more complicated, that would be my preference. And then we can have
> that mode always on.
I don't think we should bother with static keys, just always enable it
but try to reduce/group the ISBs from all the functions called on the
__switch_to() path. We may actually get a speed-up.
--
Catalin
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next prev parent reply other threads:[~2022-09-22 10:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 14:05 [PATCH 0/1] arm64: defconfig: Add Coresight as module James Clark
2022-09-21 14:05 ` [PATCH 1/1] " James Clark
2022-09-21 15:26 ` Mark Brown
2022-09-21 16:46 ` Mathieu Poirier
2022-09-22 9:04 ` James Clark
2022-09-22 9:26 ` Suzuki K Poulose
2022-09-21 15:08 ` [PATCH 0/1] " Catalin Marinas
2022-09-22 9:34 ` James Clark
2022-09-22 10:52 ` Catalin Marinas [this message]
2022-09-22 13:06 ` James Clark
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