kern/189720: [ipfw] [patch] pps action for ipfw

[bycn82]

I got it,

if the HZ=3, it always cannot meet the " 1 packet per 500ms"  perfectly. 
But if we to "X packet per Y ticks", actually the result is the same, still cannot meet the "1 packet per 500 ms" perfectly, instead, the "packet per Y ticks" will force user to use " X packet per Y*300 ms".   And the user need to understand how many millisecond each tick is .  

So I will update it this weekend. 


> -----Original Message-----
> From: owner-freebsd-ipfw at freebsd.org [mailto:owner-freebsd-
> ipfw at freebsd.org] On Behalf Of 'Luigi Rizzo'
> Sent: 29 May, 2014 23:20
> To: freebsd-ipfw at FreeBSD.org
> Subject: Re: kern/189720: [ipfw] [patch] pps action for ipfw
> 
> The following reply was made to PR kern/189720; it has been noted by
> GNATS.
> 
> From: 'Luigi Rizzo' <rizzo at iet.unipi.it>
> To: bycn82 <bycn82 at gmail.com>
> Cc: bug-followup at FreeBSD.org
> Subject: Re: kern/189720: [ipfw] [patch] pps action for ipfw
> Date: Thu, 29 May 2014 17:17:59 +0200
> 
>  On Thu, May 29, 2014 at 11:06:27PM +0800, bycn82 wrote:
>  >
>  >
>  > -----Original Message-----
>  > From: Luigi Rizzo [mailto:rizzo at iet.unipi.it]  > Sent: 29 May, 2014 22:12  > To:
> bug-followup at FreeBSD.org; bycn82 at gmail.com  > Subject: kern/189720:
> [ipfw] [patch] pps action for ipfw  >  > Hi,  > I have looked at the update from
> May 13th but it is not ready yet, the code assumes HZ=1000 so 1 tick=1ms.
>  >
>  > The translation can be done in userspace or in the kernel.
>  > I would prefer the latter.
>  > I see,
>  > If the HZ=3, that means every tick=333ms  > And if the user wants to ??? 1
> packet per 500ms???, then in the backend will not do the exactly the same as
> what user expect.
>  >
>  > Actually the implementation should be ???packets per ticks???, so how
> about this? Instead of translate it in codes. Why not update the document,
> and explain it to the user in the document ?
> 
>  'Packets per tick' this is not a useful specification  since the tick's duration is
> unknown to the user.
>  Depending on the platform you can have HZ ranging from 15-20 (on windows)
> to 10000 or even more. Normal values are 100, 250, 1000 but  you just cannot
> know what you are going to get.
> 
>  Yes there are rounding issues, and yes it is boring to write  code to handle
> them.
> 
>  luigi
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