Messages in this thread | | | Subject | Re: [PATCH V2 net 10/20] net/ena: remove redundant logic in napi callback for busy poll mode | From | Netanel Belgazal <> | Date | Mon, 5 Dec 2016 20:29:18 +0200 |
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On 12/05/2016 07:45 AM, Eric Dumazet wrote: > On Sun, 2016-12-04 at 15:19 +0200, Netanel Belgazal wrote: >> sk_busy_loop can call the napi callback few million times a sec. >> For each call there is unmask interrupt. >> We want to reduce the number of unmasks. >> >> Add an atomic variable that will tell the napi handler if >> it was called from irq context or not. >> Unmask the interrupt only from irq context. >> >> A schenario where the driver left with missed unmask isn't feasible. >> when ena_intr_msix_io is called the driver have 2 options: >> 1)Before napi completes and call napi_complete_done >> 2)After calling napi_complete_done >> >> In the former case the napi will unmask the interrupt as needed. >> In the latter case napi_complete_done will remove napi from the schedule >> list so napi will be rescheduled (by ena_intr_msix_io) and interrupt >> will be unmasked as desire in the 2nd napi call. >> >> Signed-off-by: Netanel Belgazal <netanel@annapurnalabs.com> >> --- > > This looks very complicated to me. > > I guess you missed the recent patches that happened on net-next ?
You are correct. I didn't see the patches. It is much better to use the napi_complete_done() return value. I'll rework my patch.
> > 2e713283751f494596655d9125c168aeb913f71d net/mlx4_en: use napi_complete_done() return value > 364b6055738b4c752c30ccaaf25c624e69d76195 net: busy-poll: return busypolling status to drivers > 21cb84c48ca0619181106f0f44f3802a989de024 net: busy-poll: remove need_resched() from sk_can_busy_loop() > 217f6974368188fd8bd7804bf5a036aa5762c5e4 net: busy-poll: allow preemption in sk_busy_loop() > > napi_complete_done() return code can be used by a driver, > no need to add yet another atomic operation in fast path. > > Anyway, this looks wrong : > > @@ -1186,6 +1201,7 @@ static irqreturn_t ena_intr_msix_io(int irq, void *data) > { > struct ena_napi *ena_napi = data; > > + atomic_set(&ena_napi->unmask_interrupt, 1); > napi_schedule(&ena_napi->napi); > > You probably wanted : > > if (napi_schedule_prep(n)) { > atomic_set(&ena_napi->unmask_interrupt, 1); > __napi_schedule(n); > } > > > > Please rework this napi poll using core infrastructure. > > busypoll logic should be centralized, not reimplemented in different ways in a driver. > > Thanks. > > >
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