LARTC - Jan 2005 - Could anyone explain the slot and bucket concept in SFQ to me?

Dear all,

I''m reading codes in sch_sqf.c in kernel 2.4 of Linux.
I find I messed up with the concept of slot, bucket and hash tables. Could
anyone explain the data stucture of the hash tables a little to me.

Thanks very much.

Best,
Franklin

BTW: I can not understand why the number of entries of dep[SFQ_DEPTH*]
should be twice:(

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Wang Feng wrote:
> Dear all,
> 
> I''m reading codes in sch_sqf.c in kernel 2.4 of Linux.
> I find I messed up with the concept of slot, bucket and hash tables.
I get messed up too when I read it. You can play with the values if you 
use ESFQ.

I can''t explain in detail but at high level -

Slot is linked list of packets whose IPs + src port (if TCP/UDP) hash 
into same hash bin/bucket. Slots get dequed in turn using DRR.

Hash buckets/bins (1024 of by default) is the what hash function maps 
to, to try and seperate flows. You can make it bigger with esfq so 
hopefully get less chance of different flows mapping to same bin and so 
their packets ending up being queued in same slot.

  Could
> anyone explain the data stucture of the hash tables a little to me.
> 
> Thanks very much.
> 
> Best,
> Franklin
> 
> BTW: I can not understand why the number of entries of dep[SFQ_DEPTH*]
> should be twice:(
Don''t know but esfq defines pointer rather than array here.

Andy.


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