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: 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)
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
---
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
next reply other threads:[~2018-01-10 3:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-10 3:02 Mike Galbraith [this message]
-- strict thread matches above, loose matches on Subject: below --
2018-07-17 22:21 dvb usb issues since kernel 4.9 Mauro Carvalho Chehab
2018-07-17 18:07 hannah
2018-07-17 17:09 Linus Torvalds
2018-07-17 11:54 hannah
2018-01-09 21:26 Jesper Dangaard Brouer
2018-01-09 17:55 Linus Torvalds
2018-01-09 17:42 Mauro Carvalho Chehab
2018-01-08 19:51 Linus Torvalds
2018-01-08 16:10 Alan Stern
2018-01-08 9:43 Mauro Carvalho Chehab
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1515553368.8252.5.camel@gmx.de \
--to=efault@gmx.de \
--cc=corbet@lwn.net \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=gregkh@linuxfoundation.org \
--cc=griebichler.josef@gmx.at \
--cc=hannes@redhat.com \
--cc=jbrouer@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=mchehab@s-opensource.com \
--cc=mingo@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=peterz@infradead.org \
--cc=riel@redhat.com \
--cc=stern@rowland.harvard.edu \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).