From: James Clark <james.clark@arm.com>
To: Catalin Marinas <catalin.marinas@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 14:06:42 +0100 [thread overview]
Message-ID: <489f42fc-2ec1-510b-6f3f-017ee10ee7d2@arm.com> (raw)
In-Reply-To: <Yyw+gHXLG/fXoQbT@arm.com>
On 22/09/2022 11:52, Catalin Marinas wrote:
> 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.
>
Ok thanks I will take a look at this
prev parent reply other threads:[~2022-09-22 13:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 14:05 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
2022-09-22 13:06 ` James Clark [this message]
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