netdev - Re: [Intel-wired-lan] Small Integers: Big Penalty

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Message-ID: <478248d8-559b-4324-a566-8ce691993018@molgen.mpg.de>
Date: Mon, 4 Nov 2024 10:12:14 +0100
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: David Laight <David.Laight@...LAB.COM>,
 Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
Cc: wojciech.drewek@...el.com, marcin.szycik@...el.com,
 netdev@...r.kernel.org, konrad.knitter@...el.com,
 pawel.chmielewski@...el.com, horms@...nel.org,
 intel-wired-lan@...ts.osuosl.org, pio.raczynski@...il.com,
 sridhar.samudrala@...el.com, jacob.e.keller@...el.com, jiri@...nulli.us,
 przemyslaw.kitszel@...el.com
Subject: Re: [Intel-wired-lan] Small Integers: Big Penalty

[Cc: -nex.sw.ncis.nat.hpm.dev@...el.com (550 #5.1.0 Address rejected.)]

Am 04.11.24 um 10:09 schrieb Paul Menzel:
> Dear David, dear Michal,
> 
> 
> Am 04.11.24 um 09:51 schrieb David Laight:
>> From: Michal Swiatkowski
>>> Sent: 04 November 2024 07:03
>> ...
>>>> The type of the devlink parameters msix_vec_per_pf_{min,max} is
>>>> specified as u32, so you must use value.vu32 everywhere you work with
>>>> them, not vu16.
>>>>
>>>
>>> I will change it.
>>
>> You also need a pretty good reason to use u16 anywhere at all.
>> Just because the domain of the value is small doesn't mean the
>> best type isn't [unsigned] int.
>>
>> Any arithmetic (particularly on non x86) is likely to increase
>> the code size above any perceived data saving.
> 
> In 2012 Scott Duplichan wrote *Small Integers: Big Penalty* [1]. Of 
> course you always should measure yourself.
> 
> 
> Kind regards,
> 
> Paul
> 
> 
> [1]: https://notabs.org/coding/smallIntsBigPenalty.htm