Messages in this thread | | | From | Jason Xing <> | Date | Mon, 27 Mar 2023 10:25:31 +0800 | Subject | Re: [PATCH net] net: fix raising a softirq on the current cpu with rps enabled |
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On Mon, Mar 27, 2023 at 1:35 AM Eric Dumazet <edumazet@google.com> wrote: > > > > > Forgive me. Really I need some coffee. I made a mistake. This line > > above should be: > > > > + if (!test_bit(NAPI_STATE_SCHED, &mysd->backlog.state)) > > > > But the whole thing doesn't feel right. I need a few days to dig into > > this part until Eric can help me with more of it. > > > > I am still traveling, and this is weekend time :/
Thanks for your time, Eric, really appreciate it.
> > It should not be too hard to read net/core/dev.c and remember that not > _all_ drivers (or some core networking functions) use the NAPI model. > > eg look at netif_rx() and ask yourself why your patch is buggy.
Yes, it is. In my last email I sent yesterday I encountered one issue which exactly happened when I started hundreds of iperf processes transmitting data to loopback. It got stuck :( So I realized it is the non-napi case that triggers such a problem.
> > Just look at callers of enqueue_to_backlog() and ask yourself if all > of them are called from net_rx_action() > > [The answer is no, just in case you wonder] > > In order to add your optimization, more work is needed, like adding > new parameters so that we do not miss critical > __raise_softirq_irqoff(NET_RX_SOFTIRQ) when _needed_.
Thanks, I need to do more work/study on it.
> > We keep going circles around softirq deficiencies, I feel you are > trying to fix a second-order 'issue'.
Right, going circles gives me a headache.
> > Real cause is elsewhere, look at recent patches from Jakub.
After you pointed out, I searched and found there is indeed one patchset in 2022
The tile like this:
[PATCH 0/3] softirq: uncontroversial change
Thanks, Jason
> > Thanks.
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