Messages in this thread | | | From | Eric Dumazet <> | Date | Tue, 9 May 2023 11:02:34 +0200 | Subject | Re: [PATCH] revert: "softirq: Let ksoftirqd do its job" |
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On Tue, May 9, 2023 at 3:42 AM Jakub Kicinski <kuba@kernel.org> wrote: > > On Mon, 8 May 2023 08:17:44 +0200 Paolo Abeni wrote: > > Due to the mentioned commit, when the ksoftirqd processes take charge > > of softirq processing, the system can experience high latencies. > > > > In the past a few workarounds have been implemented for specific > > side-effects of the above: > > > > commit 1ff688209e2e ("watchdog: core: make sure the watchdog_worker is not deferred") > > commit 8d5755b3f77b ("watchdog: softdog: fire watchdog even if softirqs do not get to run") > > commit 217f69743681 ("net: busy-poll: allow preemption in sk_busy_loop()") > > commit 3c53776e29f8 ("Mark HI and TASKLET softirq synchronous") > > > > but the latency problem still exists in real-life workloads, see the > > link below. > > > > The reverted commit intended to solve a live-lock scenario that can now > > be addressed with the NAPI threaded mode, introduced with commit > > 29863d41bb6e ("net: implement threaded-able napi poll loop support"), > > and nowadays in a pretty stable status. > > > > While a complete solution to put softirq processing under nice resource > > control would be preferable, that has proven to be a very hard task. In > > the short term, remove the main pain point, and also simplify a bit the > > current softirq implementation. > > > > Note that this change also reverts commit 3c53776e29f8 ("Mark HI and > > TASKLET softirq synchronous") and commit 1342d8080f61 ("softirq: Don't > > skip softirq execution when softirq thread is parking"), which are > > direct follow-ups of the feature commit. A single change is preferred to > > avoid known bad intermediate states introduced by a patch series > > reverting them individually. > > > > Link: https://lore.kernel.org/netdev/305d7742212cbe98621b16be782b0562f1012cb6.camel@redhat.com/ > > Signed-off-by: Paolo Abeni <pabeni@redhat.com> > > Tested-by: Jason Xing <kerneljasonxing@gmail.com> > > Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Thanks.
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