From: Paolo Abeni <pabeni@redhat•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: Peter Zijlstra <peterz@infradead•org>,
Hannes Frederic Sowa <hannes@stressinduktion•org>,
Eric Dumazet <edumazet@google•com>,
netdev <netdev@vger•kernel.org>,
"David S. Miller" <davem@davemloft•net>,
Jiri Pirko <jiri@mellanox•com>,
Daniel Borkmann <daniel@iogearbox•net>,
Alexei Starovoitov <ast@plumgrid•com>,
Alexander Duyck <aduyck@mirantis•com>,
Tom Herbert <tom@herbertland•com>, Ingo Molnar <mingo@kernel•org>,
Rik van Riel <riel@redhat•com>,
LKML <linux-kernel@vger•kernel.org>,
"Paul E. McKenney" <paulmck@linux•vnet.ibm.com>
Subject: Re: [RFC PATCH 0/2] net: threadable napi poll loop
Date: Thu, 12 May 2016 22:07:00 +0200 [thread overview]
Message-ID: <1463083620.5281.1.camel@redhat.com> (raw)
In-Reply-To: <1463003804.23934.154.camel@edumazet-glaptop3.roam.corp.google.com>
On Wed, 2016-05-11 at 14:56 -0700, Eric Dumazet wrote:
> On Wed, 2016-05-11 at 08:55 +0200, Peter Zijlstra wrote:
> > On Tue, May 10, 2016 at 03:51:37PM -0700, Eric Dumazet wrote:
> > > diff --git a/kernel/softirq.c b/kernel/softirq.c
> > > index 17caf4b63342..22463217e3cf 100644
> > > --- a/kernel/softirq.c
> > > +++ b/kernel/softirq.c
> > > @@ -56,6 +56,7 @@ EXPORT_SYMBOL(irq_stat);
> > > static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
> > >
> > > DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
> > > +DEFINE_PER_CPU(bool, ksoftirqd_scheduled);
> > >
> > > const char * const softirq_to_name[NR_SOFTIRQS] = {
> > > "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL",
> > > @@ -73,8 +74,10 @@ static void wakeup_softirqd(void)
> > > /* Interrupts are disabled: no need to stop preemption */
> > > struct task_struct *tsk = __this_cpu_read(ksoftirqd);
> > >
> > > - if (tsk && tsk->state != TASK_RUNNING)
> > > + if (tsk && tsk->state != TASK_RUNNING) {
> > > + __this_cpu_write(ksoftirqd_scheduled, true);
> > > wake_up_process(tsk);
> >
> > Since we're already looking at tsk->state, and the wake_up_process()
> > ensures the thing becomes TASK_RUNNING, you could add:
> >
> > static inline bool ksoftirqd_running(void)
> > {
> > return __this_cpu_read(ksoftirqd)->state == TASK_RUNNING;
here something like:
struct task_struct *tsk = __this_cpu_read(ksoftirqd);
return tsk && (tsk->state == TASK_RUNNING);
is needed since __this_cpu_read(ksoftirqd) can be NULL on boot.
> > }
>
> Indeed, and the patch looks quite simple now ;)
>
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 17caf4b63342d7839528f367b283a386413b0362..23c364485d03618773c385d943c0ef39f5931d09 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -57,6 +57,11 @@ static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp
>
> DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
>
> +static inline bool ksoftirqd_running(void)
> +{
> + return __this_cpu_read(ksoftirqd)->state == TASK_RUNNING;
> +}
> +
> const char * const softirq_to_name[NR_SOFTIRQS] = {
> "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL",
> "TASKLET", "SCHED", "HRTIMER", "RCU"
> @@ -313,7 +318,7 @@ asmlinkage __visible void do_softirq(void)
>
> pending = local_softirq_pending();
>
> - if (pending)
> + if (pending && !ksoftirqd_running())
> do_softirq_own_stack();
>
> local_irq_restore(flags);
> @@ -340,6 +345,9 @@ void irq_enter(void)
>
> static inline void invoke_softirq(void)
> {
> + if (ksoftirqd_running())
> + return;
> +
> if (!force_irqthreads) {
> #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
> /*
>
>
next prev parent reply other threads:[~2016-05-12 20:07 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-10 14:11 [RFC PATCH 0/2] net: threadable napi poll loop Paolo Abeni
2016-05-10 14:11 ` [RFC PATCH 1/2] net: implement threaded-able napi poll loop support Paolo Abeni
2016-05-10 14:11 ` [RFC PATCH 2/2] net: add sysfs attribute to control napi threaded mode Paolo Abeni
2016-05-10 14:29 ` [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet
2016-05-10 15:51 ` David Miller
2016-05-10 16:03 ` Paolo Abeni
2016-05-10 16:08 ` Eric Dumazet
2016-05-10 20:22 ` Paolo Abeni
2016-05-10 20:45 ` David Miller
2016-05-10 20:50 ` Rik van Riel
2016-05-10 20:52 ` David Miller
2016-05-10 21:01 ` Rik van Riel
2016-05-10 20:46 ` Hannes Frederic Sowa
2016-05-10 21:09 ` Eric Dumazet
2016-05-10 21:31 ` Eric Dumazet
2016-05-10 21:35 ` Rik van Riel
2016-05-10 21:53 ` Eric Dumazet
2016-05-10 22:02 ` Eric Dumazet
2016-05-10 22:44 ` Eric Dumazet
2016-05-10 22:02 ` Rik van Riel
2016-05-11 17:55 ` Eric Dumazet
2016-05-10 22:32 ` Hannes Frederic Sowa
2016-05-10 22:51 ` Eric Dumazet
2016-05-11 6:55 ` Peter Zijlstra
2016-05-11 13:13 ` Hannes Frederic Sowa
2016-05-11 14:40 ` Eric Dumazet
2016-05-11 15:01 ` Rik van Riel
2016-05-11 15:50 ` Eric Dumazet
2016-05-11 21:56 ` Eric Dumazet
2016-05-12 20:07 ` Paolo Abeni [this message]
2016-05-12 20:49 ` Eric Dumazet
2016-05-12 20:58 ` Paolo Abeni
2016-05-12 21:05 ` Eric Dumazet
2016-05-13 16:50 ` Paolo Abeni
2016-05-13 17:03 ` Eric Dumazet
2016-05-13 17:19 ` Paolo Abeni
2016-05-13 17:36 ` Eric Dumazet
2016-05-16 13:10 ` Paolo Abeni
2016-05-16 13:38 ` Eric Dumazet
2016-05-11 9:48 ` Paolo Abeni
2016-05-11 13:08 ` Eric Dumazet
2016-05-11 13:39 ` Hannes Frederic Sowa
2016-05-11 13:47 ` Hannes Frederic Sowa
2016-05-11 14:38 ` Paolo Abeni
2016-05-11 14:45 ` Eric Dumazet
2016-05-11 22:47 ` Hannes Frederic Sowa
2016-05-10 15:57 ` Thomas Gleixner
2016-05-10 20:41 ` Paolo Abeni
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