linux-kernel - Re: [PATCH v2 4/4] perf/x86/uncore: modularize Intel uncore driver

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Message-ID: <CABPqkBRihMr=+X_Gb5dSYfForTpGA6XZGfTHOA3PZNAHTJDPkg@mail.gmail.com>
Date:	Thu, 24 Apr 2014 12:36:01 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH v2 4/4] perf/x86/uncore: modularize Intel uncore driver

On Thu, Apr 24, 2014 at 12:25 PM, Yan, Zheng <zheng.z.yan@...el.com> wrote:
> On 04/24/2014 04:14 PM, Ingo Molnar wrote:
>>
>> * Stephane Eranian <eranian@...gle.com> wrote:
>>
>>>>> Most of the codes without comments are hardware specific codes.
>>>>> The corresponding contents in Intel uncore documents are big
>>>>> tables/lists, nothing tricky/interesting. I really don't know how
>>>>> to comment these code.
>>>>
>>>> Have a look at other PMU drivers, such as
>>>> arch/x86/kernel/cpu/perf_event_intel_rapl.c, which begin with a
>>>> general explanation attached below.
>>>
>>> I think a more useful modularization would be to split that huge
>>> file (perf_event_intel_uncore.c) into smaller files like we do for
>>> the core PMU. There is just too much stuff in this file for my own
>>> taste. Hard to navigate and I spend quite some time looking at it
>>> and modifying it!
>>>
>>> You could follow the model of the core PMU support files.
>>> You'd have a "core" file with the common routines, and then
>>> a file perf processor:
>>>     - perf_event_intel_uncore.c
>>>     - perf_event_intel_snbep_uncore.c
>>>     - perf_event_intel_nhmex_uncore.c
>>>     - perf_event_intel_ivt_uncore.c
>>>     - ...
>>>
>>> Each processor specific module, would be a kernel module. The core
>>> could be one too. Note that this would not alleviate the need for
>>> some basic descriptions at the beginning of each file outlining the
>>> PMU boxes exported to a minimum.
>
> Most of hardware specific codes in the Intel uncore driver are for SandyBridge/IvyBridge/Haswell. Uncore subsystem in these CPUs are similar. One module per CPU type means we have to duplicate lots of code. I don't think it's a good idea.
>
Then, at least split nhm_ex from the rest. It is very big.

> Regards
> Yan, Zheng
>
>>
>> This structure you outline sounds like a good first step, I like it.
>>
>> To simplify this restructuring, initially we could even keep the core
>> uncore bits in the core (ha!), to not have module-on-module
>> dependencies.
>>
>> Thanks,
>>
>>       Ingo
>>
>
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