From: Mike Galbraith <efault@gmx.de>
To: Jesper Dangaard Brouer <jbrouer@redhat.com>,
Mauro Carvalho Chehab <mchehab@s-opensource.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Alan Stern <stern@rowland.harvard.edu>,
Ingo Molnar <mingo@kernel.org>,
Josef Griebichler <griebichler.josef@gmx.at>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
USB list <linux-usb@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
Rik van Riel <riel@redhat.com>, Paolo Abeni <pabeni@redhat.com>,
Hannes Frederic Sowa <hannes@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>, Jonathan Corbet <corbet@lwn.net>,
LMML <linux-media@vger.kernel.org>,
David Miller <davem@davemloft.net>
Subject: Re: dvb usb issues since kernel 4.9
Date: Wed, 10 Jan 2018 04:02:48 +0100 [thread overview]
Message-ID: <1515553368.8252.5.camel@gmx.de> (raw)
In-Reply-To: <20180109222604.64d4377c@redhat.com>
On Tue, 2018-01-09 at 22:26 +0100, Jesper Dangaard Brouer wrote:
>
> I've previously experienced that you can be affected by the scheduler
> granularity, which is adjustable (with CONFIG_SCHED_DEBUG=y):
>
> $ grep -H . /proc/sys/kernel/sched_*_granularity_ns
> /proc/sys/kernel/sched_min_granularity_ns:2250000
> /proc/sys/kernel/sched_wakeup_granularity_ns:3000000
>
> The above numbers were confirmed on the RPi2 (see[2]). With commit
> 4cd13c21b207 ("softirq: Let ksoftirqd do its job"), I expect/assume that
> softirq processing latency is bounded by the sched_wakeup_granularity_ns,
> which with 3 ms is not good enough for their use-case.
Note of caution wrt twiddling sched_wakeup_granularity_ns: it must
remain < sched_latency_ns/2 else you effectively disable wakeup
preemption completely, turning CFS into a tick granularity scheduler.
-Mike
next prev parent reply other threads:[~2018-01-10 3:02 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <trinity-35b3a044-b548-4a31-9646-ed9bc83e6846-1513505978471@3c-app-gmx-bs03>
[not found] ` <20171217120634.pmmuhdqyqmbkxrvl@gofer.mess.org>
[not found] ` <20171217112738.4f3a4f9b@recife.lan>
[not found] ` <trinity-1fa14556-8596-44b1-95cb-b8919d94d2d4-1515251056328@3c-app-gmx-bs15>
2018-01-06 19:54 ` dvb usb issues since kernel 4.9 Mauro Carvalho Chehab
2018-01-06 21:07 ` Aw: " Josef Griebichler
2018-01-06 21:44 ` Alan Stern
2018-01-07 11:03 ` Mauro Carvalho Chehab
2018-01-07 15:41 ` Alan Stern
[not found] ` <Pine.LNX.4.44L0.1801071010540.13425-100000-pYrvlCTfrz9XsRXLowluHWD2FQJk+8+b@public.gmane.org>
2018-01-07 17:01 ` Aw: " Josef Griebichler
2018-01-08 9:43 ` Mauro Carvalho Chehab
2018-01-08 16:10 ` Alan Stern
2018-01-08 16:26 ` Aw: " Josef Griebichler
2018-01-08 16:31 ` Alan Stern
2018-01-08 17:15 ` Aw: " Josef Griebichler
2018-01-08 17:35 ` Alan Stern
2018-01-08 20:40 ` Jesper Dangaard Brouer
2018-01-08 21:31 ` Jesper Dangaard Brouer
2018-01-08 21:44 ` Peter Zijlstra
2018-01-08 22:16 ` Jesper Dangaard Brouer
2018-01-09 16:51 ` Aw: " Josef Griebichler
2018-01-09 17:27 ` Eric Dumazet
2018-01-09 17:48 ` Linus Torvalds
2018-01-09 17:57 ` Eric Dumazet
2018-01-09 18:58 ` Linus Torvalds
2018-01-09 21:48 ` Eric Dumazet
2018-01-10 9:45 ` Jesper Dangaard Brouer
2018-01-12 21:13 ` Mauro Carvalho Chehab
2018-01-12 21:48 ` Eric Dumazet
2018-01-13 9:09 ` Mauro Carvalho Chehab
2018-01-13 10:46 ` Mauro Carvalho Chehab
2018-01-07 21:23 ` Linus Torvalds
2018-01-08 10:02 ` Mauro Carvalho Chehab
2018-01-08 11:59 ` Jesper Dangaard Brouer
2018-01-08 12:53 ` Mauro Carvalho Chehab
2018-01-08 16:25 ` Alan Stern
2018-01-08 17:55 ` Ingo Molnar
2018-01-08 18:32 ` Linus Torvalds
2018-01-08 19:15 ` Alan Stern
2018-01-08 19:51 ` Linus Torvalds
2018-01-09 17:42 ` Mauro Carvalho Chehab
2018-01-09 17:55 ` Linus Torvalds
2018-01-09 21:26 ` Jesper Dangaard Brouer
2018-01-10 3:02 ` Mike Galbraith [this message]
2018-07-17 11:54 ` Hanna Hawa
2018-07-17 17:09 ` Linus Torvalds
2018-07-17 18:07 ` Hanna Hawa
2018-07-17 22:21 ` Mauro Carvalho Chehab
2018-01-26 14:17 ` Mauro Carvalho Chehab
2018-01-26 19:37 ` Mauro Carvalho Chehab
2018-01-29 13:51 ` Mauro Carvalho Chehab
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