Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 9 Jan 2018 10:58:30 -0800 | Subject | Re: Re: dvb usb issues since kernel 4.9 |
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On Tue, Jan 9, 2018 at 9:57 AM, Eric Dumazet <edumazet@google.com> wrote: > > Your patch considers TASKLET_SOFTIRQ being a candidate for 'immediate > handling', but TCP Small queues heavily use TASKLET, > so as far as I am concerned a revert would have the same effect.
Does it actually?
TCP ends up dropping packets outside of the window etc, so flooding a machine with TCP packets and causing some further processing up the stack sounds very different from the basic packet flooding thing that happens with NET_RX_SOFTIRQ.
Also, honestly, the kinds of people who really worry about flooding tend to have packet filtering in the receive path etc.
So I really think "you can use up 90% of CPU time with a UDP packet flood from the same network" is very very very different - and honestly not at all as important - as "you want to be able to use a USB DVB receiver and watch/record TV".
Because that whole "UDP packet flood from the same network" really is something you _fundamentally_ have other mitigations for.
I bet that whole commit was introduced because of a benchmark test, rather than real life. No?
In contrast, now people are complaining about real loads not working.
Linus
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