From: David Miller <davem@davemloft.net>
To: bigeasy@linutronix.de
Cc: edumazet@google.com, netdev@vger.kernel.org, tglx@linutronix.de
Subject: Re: [PATCH 1/2] net/core: use local_bh_disable() in netif_rx_ni()
Date: Tue, 20 Jun 2017 13:08:40 -0400 (EDT) [thread overview]
Message-ID: <20170620.130840.472295224655944129.davem@davemloft.net> (raw)
In-Reply-To: <20170616172400.10809-1-bigeasy@linutronix.de>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 16 Jun 2017 19:23:59 +0200
> In 2004 [0] netif_rx_ni() gained a preempt_disable() section around
> netif_rx() and its do_softirq() + testing for it. The do_softirq() part
> is required because netif_rx() raises the softirq but does not invoke
> it. The preempt_disable() is required to avoid running the BH in
> parallel.
> All this can be avoided be putting this into a local_bh_disable()ed
> section. The local_bh_enable() part will invoke do_softirq() if
> required.
>
> [0] Make netif_rx_ni preempt-safe
> http://oss.sgi.com/projects/netdev/archive/2004-10/msg02211.html
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Why make extra work? The current code is cheaper.
Doing all of that dance with the local_bh_enable() function call is
more expensive than the inlined counter bump and softirq state
check.
I'm not applying this without a better justification, sorry.
prev parent reply other threads:[~2017-06-20 17:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-16 17:23 [PATCH 1/2] net/core: use local_bh_disable() in netif_rx_ni() Sebastian Andrzej Siewior
2017-06-16 17:24 ` [PATCH 2/2] net/core: remove explicit do_softirq() from busy_poll_stop() Sebastian Andrzej Siewior
2017-06-20 17:09 ` David Miller
2017-06-20 17:08 ` David Miller [this message]
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