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Re: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events

Started byWill Deacon <will.deacon@arm.com>
First post2016-02-15 20:50 +0100
Last post2016-02-18 14:50 +0100
Articles 5 — 2 participants

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  Re: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events Will Deacon <will.deacon@arm.com> - 2016-02-15 20:50 +0100
    Re: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events Will Deacon <will.deacon@arm.com> - 2016-02-15 21:10 +0100
      Re: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events Jan Glauber <jan.glauber@caviumnetworks.com> - 2016-02-18 10:30 +0100
        Re: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events Will Deacon <will.deacon@arm.com> - 2016-02-18 12:30 +0100
          Re: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events Jan Glauber <jan.glauber@caviumnetworks.com> - 2016-02-18 14:50 +0100

#1334768 — Re: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events

FromWill Deacon <will.deacon@arm.com>
Date2016-02-15 20:50 +0100
SubjectRe: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events
Message-ID<r2xjJ-5z4-35@gated-at.bofh.it>
On Wed, Feb 03, 2016 at 06:11:56PM +0100, Jan Glauber wrote:
> The implemented Cortex A57 events are not A57 specific.
> They are recommended by ARM and can be found on other
> ARMv8 SOCs like Cavium ThunderX too. Therefore move
> these events to the common PMUv3 table.

I can't find anything in the architecture that suggests these event
numbers are necessarily portable between implementations. Am I missing
something?

Will

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#1334782

FromWill Deacon <will.deacon@arm.com>
Date2016-02-15 21:10 +0100
Message-ID<r2xD4-5Wh-17@gated-at.bofh.it>
In reply to#1334768
On Mon, Feb 15, 2016 at 07:40:37PM +0000, Will Deacon wrote:
> On Wed, Feb 03, 2016 at 06:11:56PM +0100, Jan Glauber wrote:
> > The implemented Cortex A57 events are not A57 specific.
> > They are recommended by ARM and can be found on other
> > ARMv8 SOCs like Cavium ThunderX too. Therefore move
> > these events to the common PMUv3 table.
> 
> I can't find anything in the architecture that suggests these event
> numbers are necessarily portable between implementations. Am I missing
> something?

Aha, I just noticed appendix K3.1 (silly me for missing it...).

Lemme check whether or not that mandates that those encodings can't be
used for wildly different things.

Will

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#1337191

FromJan Glauber <jan.glauber@caviumnetworks.com>
Date2016-02-18 10:30 +0100
Message-ID<r3t4n-3rL-31@gated-at.bofh.it>
In reply to#1334782
On Mon, Feb 15, 2016 at 08:06:13PM +0000, Will Deacon wrote:
> On Mon, Feb 15, 2016 at 07:40:37PM +0000, Will Deacon wrote:
> > On Wed, Feb 03, 2016 at 06:11:56PM +0100, Jan Glauber wrote:
> > > The implemented Cortex A57 events are not A57 specific.
> > > They are recommended by ARM and can be found on other
> > > ARMv8 SOCs like Cavium ThunderX too. Therefore move
> > > these events to the common PMUv3 table.
> > 
> > I can't find anything in the architecture that suggests these event
> > numbers are necessarily portable between implementations. Am I missing
> > something?
> 
> Aha, I just noticed appendix K3.1 (silly me for missing it...).
> 
> Lemme check whether or not that mandates that those encodings can't be
> used for wildly different things.

To me it looks like we would just have duplicated code without the patch,
and at least the event types (e.g. L1D_CACHE_RD) should be identical
across implementations.

But I don't care too much, so please tell me if should drop the patch or
keep it.

thanks,
Jan

> Will

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#1337287

FromWill Deacon <will.deacon@arm.com>
Date2016-02-18 12:30 +0100
Message-ID<r3uWu-4Ju-7@gated-at.bofh.it>
In reply to#1337191
On Thu, Feb 18, 2016 at 10:13:07AM +0100, Jan Glauber wrote:
> On Mon, Feb 15, 2016 at 08:06:13PM +0000, Will Deacon wrote:
> > On Mon, Feb 15, 2016 at 07:40:37PM +0000, Will Deacon wrote:
> > > On Wed, Feb 03, 2016 at 06:11:56PM +0100, Jan Glauber wrote:
> > > > The implemented Cortex A57 events are not A57 specific.
> > > > They are recommended by ARM and can be found on other
> > > > ARMv8 SOCs like Cavium ThunderX too. Therefore move
> > > > these events to the common PMUv3 table.
> > > 
> > > I can't find anything in the architecture that suggests these event
> > > numbers are necessarily portable between implementations. Am I missing
> > > something?
> > 
> > Aha, I just noticed appendix K3.1 (silly me for missing it...).
> > 
> > Lemme check whether or not that mandates that those encodings can't be
> > used for wildly different things.
> 
> To me it looks like we would just have duplicated code without the patch,
> and at least the event types (e.g. L1D_CACHE_RD) should be identical
> across implementations.
> 
> But I don't care too much, so please tell me if should drop the patch or
> keep it.

Tell you what then -- how about we simply rename those to ARMV8_IMPDEF_*
instead of ARMV8_A57_*? That way, we can easily identify them as distinct
from the architected events if we need to in future.

Will

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#1337365

FromJan Glauber <jan.glauber@caviumnetworks.com>
Date2016-02-18 14:50 +0100
Message-ID<r3x7Y-6f7-11@gated-at.bofh.it>
In reply to#1337287
On Thu, Feb 18, 2016 at 11:24:29AM +0000, Will Deacon wrote:
> On Thu, Feb 18, 2016 at 10:13:07AM +0100, Jan Glauber wrote:
> > On Mon, Feb 15, 2016 at 08:06:13PM +0000, Will Deacon wrote:
> > > On Mon, Feb 15, 2016 at 07:40:37PM +0000, Will Deacon wrote:
> > > > On Wed, Feb 03, 2016 at 06:11:56PM +0100, Jan Glauber wrote:
> > > > > The implemented Cortex A57 events are not A57 specific.
> > > > > They are recommended by ARM and can be found on other
> > > > > ARMv8 SOCs like Cavium ThunderX too. Therefore move
> > > > > these events to the common PMUv3 table.
> > > > 
> > > > I can't find anything in the architecture that suggests these event
> > > > numbers are necessarily portable between implementations. Am I missing
> > > > something?
> > > 
> > > Aha, I just noticed appendix K3.1 (silly me for missing it...).
> > > 
> > > Lemme check whether or not that mandates that those encodings can't be
> > > used for wildly different things.
> > 
> > To me it looks like we would just have duplicated code without the patch,
> > and at least the event types (e.g. L1D_CACHE_RD) should be identical
> > across implementations.
> > 
> > But I don't care too much, so please tell me if should drop the patch or
> > keep it.
> 
> Tell you what then -- how about we simply rename those to ARMV8_IMPDEF_*
> instead of ARMV8_A57_*? That way, we can easily identify them as distinct
> from the architected events if we need to in future.

Sounds good. I'll refresh and re-post the whole series then.

Jan

> Will

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