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Date:      Wed, 3 Jan 2018 14:12:00 -0800
From:      Nathan Whitehorn <nwhitehorn@freebsd.org>
To:        freebsd-current@freebsd.org
Subject:   Re: Programmatically cache line
Message-ID:  <35d2d373-92f1-499f-f470-e4528b08b937@freebsd.org>
In-Reply-To: <CABh_MK=2uvPoNCg7qL14yVuxo_%2BHVSvccLTBAnRAHNzqor--0g@mail.gmail.com>
References:  <CALM2mEmWYz5nyqvxMJwMWoFOXnDTvWFrEug7UUha6xe7Um6ODw@mail.gmail.com> <20171230082812.GL1684@kib.kiev.ua> <CAJ-VmomxGJsn8eOtWoqevdW-spUPgcSGKEc7eR4xuXLP-E1XRA@mail.gmail.com> <08038E36-9679-4286-9083-FCEDD637ADCC@FreeBSD.org> <20180101103655.GF1684@kib.kiev.ua> <CABh_MK=2uvPoNCg7qL14yVuxo_%2BHVSvccLTBAnRAHNzqor--0g@mail.gmail.com>

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On 01/03/18 13:37, Ed Schouten wrote:
> 2018-01-01 11:36 GMT+01:00 Konstantin Belousov <kostikbel@gmail.com>:
>>>>> On x86, the CPUID instruction leaf 0x1 returns the information in
>>>>> %ebx register.
>>>> Hm, weird. Why don't we extend sysctl to include this info?
>> For the same reason we do not provide a sysctl to add two integers.
> I strongly agree with Kostik on this one. Why add stuff to the kernel,
> if userspace is already capable of extracting this? Adding that stuff
> to sysctl has the downside that it will effectively introduce yet
> another FreeBSDism, whereas something generic already exists.
>

Well, kind of. The userspace version is platform-dependent and not 
always available: for example, on PPC, you can't do this from userland 
and we provide a sysctl machdep.cacheline_size to userland. It would be 
nice to have an MI API.
-Nathan



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