From: Eric Dumazet <edumazet@google.com>
To: Paolo Abeni <pabeni@redhat.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 10:03:42 -0700 [thread overview]
Message-ID: <CANn89iLxx-K6XDgU=c+6S1ExtSoCqQyG+7XjzJW+xoL3ACJYuQ@mail.gmail.com> (raw)
In-Reply-To: <1463158203.11721.25.camel@redhat.com>
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 ?
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.
I noticed that simply doing a "ping -n gateway" while the UDP flood
was occurring, my udp receiver had quite a different efficiency.
Thanks.
next prev parent reply other threads:[~2016-05-13 17:03 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 [this message]
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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