linux-kernel - Re: [PATCH 0/3] arm64: perf: add support for Cortex-A55/A75/A76

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Date:   Mon, 6 Jul 2020 16:04:11 +0800
From:   Jisheng Zhang <Jisheng.Zhang@...aptics.com>
To:     Will Deacon <will@...nel.org>
Cc:     Robin Murphy <robin.murphy@....com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] arm64: perf: add support for Cortex-A55/A75/A76

Hi Will,

On Fri, 3 Jul 2020 13:33:47 +0100 Will Deacon wrote:

> 
> 
> On Fri, Jun 19, 2020 at 06:44:37PM +0800, Jisheng Zhang wrote:
> > The Cortex-A55/A75/A76 use some implementation defined perf events.
> > Add the support.
> >
> > Jisheng Zhang (3):
> >   arm64: perf: add support for Cortex-A55
> >   arm64: perf: add support for Cortex-A75
> >   arm64: perf: add support for Cortex-A76
> >
> >  arch/arm64/kernel/perf_event.c | 49 +++++++++++++++++++++++++++++++---
> >  1 file changed, 45 insertions(+), 4 deletions(-)  
> 
> Do we really need this? I'd prefer for this stuff to live in userspace

IMHO, this stuff is to add a relationship between linux standard
HW events and ARM PMU events, take CA55 for example:

w/o the stuff, perf -e PREFETCH_LINEFILL

w/ the stuff, perf -e L1-dcache-prefetch-misses

But indeed, we also need to add json descriptions in perf tool, I'll submit
patches.

Thanks

> now that the perf tool has supported JSON event descriptions for a while,
> and the in-kernel driver advertises the architected events advertised
> by PMCEID*.
> 
> Will