Hi Felix,
On Oct 1, 2012, at 10:26 , Felix Fietkau wrote:
> On 2012-10-01 6:49 PM, Dave Täht wrote:
>> From: Dave Taht <dave.t...@bufferbloat.net>
>>
>> After queue lengths start getting out of hand, try to preserve memory
>> by shortening skbs to their truesize on the common pfifo, codel, and
>> fq_codel qdiscs.
>>
>> Arguably (128) should be a configureable param
> I think this is a bad idea, at least on routers. 'Preserving memory'
> here involves copying buffer data, which is really horrible for
> performance. The memory bus is a tough bottleneck when routing at high
> speed…
But the in severe situations the alternative is OOM -> watchdog based
reboot; under these circumstances limping along and recover later once the
memory pressure is over sounds better than rebooting? (At least in cerowrt the
OOM reboot cycle could be easily initiated by a simple UDP flood through the
router. Now, while this is abusive, it is way better if the router survives
this and recovers with out a reboot, IMHO). This change along with a few others
Dave made turned cerowrt robust against UDP flooding which I think is the right
thing to do. Since this only triggers once memory gets scarce, think of this as
a defense mechanism in a situation where performance will suffer anyway...
best
Sebastian
>
> - Felix
>
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