Re: old top and new -current: missing arcstat sysctl

From: Allan Jude <allanjude_at_freebsd.org>
Date: Wed, 29 Aug 2018 13:52:32 -0400
On 2018-08-29 11:18, Mark Johnston wrote:
> On Wed, Aug 29, 2018 at 07:44:31AM +0200, Alexander Leidinger wrote:
>>
>> Quoting Mark Johnston <markj_at_freebsd.org> (from Tue, 28 Aug 2018  
>> 10:48:42 -0400):
>>
>>> On Tue, Aug 28, 2018 at 10:25:39AM -0400, Allan Jude wrote:
>>>> On 2018-08-28 02:40, Alexander Leidinger wrote:
>>>>> Hi,
>>>>>
>>>>> top reports missing sysctl kstat.zfs.misc.arcstats.other_size for
>>>>> 12.0-alpha3 with a top from an old-ish -current.
>>>>>
>>>>> Is/will this be handled via a compat-11 sysctl (my kernel is without
>>>>> compat-xx), or did this slip through?
>>
>>>> That is not something that a compat-xx package can handle.
>>>
>>> s/package/kernel option/?
>>
>> Sorry, the COMPAT_FREEBSDx kernel options was what I had in mind when  
>> I wrote this.
>>
>>>> That arcstat was broken up into 3 individual stats, which the
>>>> 12.0-alpha3 version of top will sum together for you.
>>>>
>>>> I don't think we've had compat shims like this for previous versions of
>>>> top, I recall having similar issues when the 'laundry' counter was
>>>> introduced.
>>>
>>> IIRC that would have been the inverted case of running a newer top(1)
>>> with an older kernel lacking the v_laundry_pages sysctl.  In general I'd
>>> expect us to support running an older top(1) with newer kernels if we
>>> don't have to bend over backwards to provide compatibility.
>>
>> If the new top is summing the 3 up anyway, it sounds like we could  
>> provide the old one as backwards compatibility, even if it is  
>> redundant. I rather have an redundant counter and an old top working  
>> (in the generic case of what we promise to our users; in this specific  
>> case for me I just need to get around to update the jails on the  
>> corresponding systems), than bailing out without displaying anything.
> 
> I'm inclined to agree, especially since this (running older top(1)s) has
> come up before when I removed some VM sysctls:
> https://reviews.freebsd.org/D16943
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I misunderstood previously (COMPAT_FREEBSDxx vs the compat-xx package).
I am in agreement with Mark about fixing this for 12.0

-- 
Allan Jude


Received on Wed Aug 29 2018 - 15:52:43 UTC

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