On 10.10.2020 17:22, Jakub Kicinski wrote: > On Sat, 10 Oct 2020 15:08:15 +0200 Heiner Kallweit wrote: >> On 09.10.2020 18:06, Heiner Kallweit wrote: >>> On 09.10.2020 17:58, Jakub Kicinski wrote: >>>> On Fri, 9 Oct 2020 16:54:06 +0200 Heiner Kallweit wrote: >>>>> I'm thinking about a __napi_schedule version that disables hard irq's >>>>> conditionally, based on variable force_irqthreads, exported by the irq >>>>> subsystem. This would allow to behave correctly with threadirqs set, >>>>> whilst not loosing the _irqoff benefit with threadirqs unset. >>>>> Let me come up with a proposal. >>>> >>>> I think you'd need to make napi_schedule_irqoff() behave like that, >>>> right? Are there any uses of napi_schedule_irqoff() that are disabling >>>> irqs and not just running from an irq handler? >>>> >>> Right, the best approach depends on the answer to the latter question. >>> I didn't check this yet, therefore I described the least intrusive approach. >>> >> >> With some help from coccinelle I identified the following functions that >> call napi_schedule_irqoff() or __napi_schedule_irqoff() and do not run >> from an irq handler (at least not at the first glance). >> >> dpaa2_caam_fqdan_cb >> qede_simd_fp_handler >> mlx4_en_rx_irq >> mlx4_en_tx_irq > > Don't know the others but FWIW the mlx4 ones run from an IRQ handler, > AFAICT: > > static irqreturn_t mlx4_interrupt(int irq, void *dev_ptr) > static irqreturn_t mlx4_msi_x_interrupt(int irq, void *eq_ptr) > mlx4_eq_int() > mlx4_cq_completion > cq->comp() > >> qeth_qdio_poll >> netvsc_channel_cb >> napi_watchdog > > This one runs from a hrtimer, which I believe will be a hard irq > context on anything but RT. I could be wrong. >
A similar discussion can be found e.g. here: https://lore.kernel.org/netdev/20191126222013.1904785-1-bige...@linutronix.de/ However I don't see any actual outcome.
