From: Paolo Abeni <pabeni@redhat•com>
To: Eric Dumazet <edumazet@google•com>
Cc: Eric Dumazet <eric.dumazet@gmail•com>,
Peter Zijlstra <peterz@infradead•org>,
Hannes Frederic Sowa <hannes@stressinduktion•org>,
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: Fri, 13 May 2016 19:19:00 +0200 [thread overview]
Message-ID: <1463159940.11721.37.camel@redhat.com> (raw)
In-Reply-To: <CANn89iLxx-K6XDgU=c+6S1ExtSoCqQyG+7XjzJW+xoL3ACJYuQ@mail.gmail.com>
On Fri, 2016-05-13 at 10:03 -0700, Eric Dumazet wrote:
> On Fri, May 13, 2016 at 9:50 AM, Paolo Abeni <pabeni@redhat•com> wrote:
>
> >> 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
> >> /*
> >
> > In this version of the path, the chunk affecting __local_bh_enable_ip()
> > has been removed.
> >
> > I think it is beneficial, because it allows avoiding a
> > local_irq_save()/local_irq_restore() pairs per local_bh_enable under heavy load.
> >
>
> Interesting, do you have any numbers ?
The difference is small, in the noise range:
[with this patch applied]
super_netperf 100 -H 192.168.122.1 -t UDP_STREAM -l 60 -- -m 1
9.00
[adding the test into __local_bh_enable_ip(), too]
super_netperf 100 -H 192.168.122.1 -t UDP_STREAM -l 60 -- -m 1
9.14
but reproducible, in my experiments.
I have similar data for different number of flows.
> I believe I did this so that we factorize the logic in do_softirq()
> and keep the code local to kernel/softirq.c
>
> Otherwise, netif_rx_ni() could also process softirq while ksoftirqd
> was scheduled,
> so I would have to 'export' the ksoftirqd_running(void) helper in an
> include file.
The idea could be to add the test in __local_bh_enable_ip(), maintaining
the test also in do_softirq() (as currently done, i.e for
local_softirq_pending())
Cheers,
Paolo
next prev parent reply other threads:[~2016-05-13 17:19 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
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 [this message]
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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