[RFC 0/7] Add support to process rx packets in thread
Hillf Danton
hdanton at sina.com
Sat Jul 25 10:57:28 EDT 2020
On Sat, 25 Jul 2020 16:08:41 +0200 Sebastian Gottschall wrote:
> Am 25.07.2020 um 14:25 schrieb Hillf Danton:
> > On Sat, 25 Jul 2020 12:38:00 +0200 Sebastian Gottschall wrote:
> >> you may consider this
> >>
> >> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1142611.html
> >>
> >> <https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1142611.html>
> >>
> > Thanks very much for your link.
> >
> >> years ago someone already wanted to bring this feature upstream, but it
> >> was denied. i already tested this patch the last 2 days and it worked so
> >> far (with some little modifications)
> >> so such a solution existed already and may be considered here
> >
> > I don't see outstanding difference in principle from Paolo's work in
> > 2016 except for the use of kthread_create() and friends because kworker
> > made use of them even before 2016. This is a simpler one as shown by
> > the diff stat in his cover letter.
> >
> i agree. i just can say that i tested this patch recently due this
> discussion here. and it can be changed by sysfs. but it doesnt work for
> wifi drivers which are mainly using dummy netdev devices. for this i
> made a small patch to get them working using napi_set_threaded manually
> hardcoded in the drivers. (see patch bellow)
By CONFIG_THREADED_NAPI, there is no need to consider what you did here
in the napi core because device drivers know better and are responsible
for it before calling napi_schedule(n).
> i also tested various networking drivers. one thing i notice doesnt
> work. some napi code is used for tx polling. so from my experience this
> concept just works good for rx with the most drivers.
Drivers are also taking care of the napi::poll cb before calling
netif_threaded_napi_add(), while the core offers napi threads. But these
are the trivial differences from the 2016 RFC AFAICS.
> so far i tested mt76, ath10k and some soc ethernet chipsets with good
> success. on ath10k i had about 10 - 20% performance gain on multicore
> systems. using standard iperf3 with 4 parallel streams.
Thanks for sharing the tests.
>
> -5439,7 +5441,7 @@ int napi_set_threaded(struct napi_struct *n, bool
> clear_bit(NAPI_STATE_THREADED, &n->state);
>
> /* if the device is initializing, nothing todo */
> - if (test_bit(__LINK_STATE_START, &n->dev->state))
> + if (test_bit(__LINK_STATE_START, &n->dev->state) &&
> n->dev->reg_state != NETREG_DUMMY)
> return 0;
>
> napi_thread_stop(n);
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