From: Peter Hurley <peter@hurleysoftware.com>
To: David Miller <davem@davemloft.net>
Cc: eric.dumazet@gmail.com, edumazet@google.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
gregkh@linuxfoundation.org, dmaengine@vger.kernel.org,
john.ogness@linutronix.de, bigeasy@linutronix.de,
akpm@linux-foundation.org
Subject: Re: Softirq priority inversion from "softirq: reduce latencies"
Date: Sat, 27 Feb 2016 15:33:58 -0800 [thread overview]
Message-ID: <56D23266.2080306@hurleysoftware.com> (raw)
In-Reply-To: <20160227.180403.2101360385050644823.davem@davemloft.net>
On 02/27/2016 03:04 PM, David Miller wrote:
> From: Peter Hurley <peter@hurleysoftware.com>
> Date: Sat, 27 Feb 2016 12:29:39 -0800
>
>> Not really. softirq raised from interrupt context will always execute
>> on this cpu and not in ksoftirqd, unless load forces softirq loop abort.
>
> That guarantee never was specified.
??
Neither is running network socket servers at normal priority as if they're
higher priority than softirq.
> Or are you saying that by design, on a system under load, your UART
> will not function properly?
>
> Surely you don't mean that.
No, that's not what I mean.
What I mean is that bypassing the entire SOFTIRQ priority so that
sshd can process one network packet makes a mockery of the point of softirq.
This hack to workaround NET_RX looping over-and-over-and-over affects every
subsystem, not just one uart.
HI, TIMER, BLOCK; all of these are skipped: that's straight-up, a bug.
Regards,
Peter Hurley
next prev parent reply other threads:[~2016-02-27 23:34 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-27 18:19 Softirq priority inversion from "softirq: reduce latencies" Peter Hurley
2016-02-27 20:13 ` Eric Dumazet
2016-02-27 20:29 ` Peter Hurley
2016-02-27 23:04 ` David Miller
2016-02-27 23:33 ` Peter Hurley [this message]
2016-02-28 1:59 ` Eric Dumazet
2016-02-28 2:10 ` Peter Hurley
2016-02-28 2:17 ` Eric Dumazet
2016-02-28 4:46 ` David Miller
2016-02-28 5:55 ` Mike Galbraith
2016-02-28 17:01 ` Francois Romieu
2016-02-29 4:58 ` Mike Galbraith
2016-02-29 15:03 ` Peter Hurley
2016-02-29 15:19 ` Eric Dumazet
2016-02-29 15:54 ` Peter Hurley
2016-02-29 16:21 ` Eric Dumazet
2016-02-29 18:05 ` Peter Hurley
2016-02-29 18:24 ` Eric Dumazet
2016-02-29 18:53 ` Peter Hurley
2016-02-29 19:14 ` Thomas Gleixner
2016-02-29 20:24 ` David Miller
2016-02-29 23:04 ` Peter Hurley
2016-02-29 15:27 ` Eric Dumazet
2016-02-29 19:13 ` Peter Hurley
2016-02-29 19:43 ` Eric Dumazet
2016-02-29 15:40 ` Mike Galbraith
2016-02-29 15:58 ` Peter Hurley
2016-02-29 16:24 ` Eric Dumazet
2016-02-29 17:16 ` David Miller
2016-03-07 15:31 ` Sebastian Andrzej Siewior
2016-03-07 17:06 ` Mike Galbraith
2016-03-07 15:48 ` Sebastian Andrzej Siewior
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