From: Jesper Dangaard Brouer <jbrouer@redhat.com> To: 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: Tue, 9 Jan 2018 22:26:04 +0100 [thread overview] Message-ID: <20180109222604.64d4377c@redhat.com> (raw) In-Reply-To: <20180109154235.2a42f0a0@vento.lan> On Tue, 9 Jan 2018 15:42:35 -0200 Mauro Carvalho Chehab <mchehab@s-opensource.com> wrote: > Em Mon, 8 Jan 2018 11:51:04 -0800 Linus Torvalds <torvalds@linux-foundation.org> escreveu: > [...] > Patch makes sense to me, although I was not able to test it myself. The patch also make sense to me. I've done some basic testing with it on my high-end Broadwell system (that I use for 100Gbit/s testing). As expected the network overload case still works, as NET_RX_SOFTIRQ is not matched. > I set a RPi3 machine here with vanilla Kernel 4.14.11 running a > standard raspbian distribution (with elevator=deadline). I found a Raspberry Pi Model B+ (I think, BCM2835), that I loaded the LibreELEC distro on. One of the guys even created an image for me with a specific kernel[1] (that I just upgraded the system with). [1] https://forum.libreelec.tv/thread/4235-dvb-issue-since-le-switched-to-kernel-4-9-x/?postID=77031#post77031 > My plan is to do more tests along this week, and try to tweak a little > bit both userspace and kernelspace, in order to see if I can get > better results. 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. Thus, if you manage to reproduce the case, try to see if adjusting this can mitigate the issue... Their system have non-preempt kernel, should they use PREEMPT? LibreELEC:~ # uname -a Linux LibreELEC 4.14.10 #1 SMP Tue Jan 9 17:35:03 GMT 2018 armv7l GNU/Linux [2] https://forum.libreelec.tv/thread/4235-dvb-issue-since-le-switched-to-kernel-4-9-x/?postID=76999#post76999 -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
WARNING: multiple messages have this Message-ID (diff)
From: Jesper Dangaard Brouer <jbrouer@redhat.com> To: 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: Tue, 9 Jan 2018 22:26:04 +0100 [thread overview] Message-ID: <20180109222604.64d4377c@redhat.com> (raw) On Tue, 9 Jan 2018 15:42:35 -0200 Mauro Carvalho Chehab <mchehab@s-opensource.com> wrote: > Em Mon, 8 Jan 2018 11:51:04 -0800 Linus Torvalds <torvalds@linux-foundation.org> escreveu: > [...] > Patch makes sense to me, although I was not able to test it myself. The patch also make sense to me. I've done some basic testing with it on my high-end Broadwell system (that I use for 100Gbit/s testing). As expected the network overload case still works, as NET_RX_SOFTIRQ is not matched. > I set a RPi3 machine here with vanilla Kernel 4.14.11 running a > standard raspbian distribution (with elevator=deadline). I found a Raspberry Pi Model B+ (I think, BCM2835), that I loaded the LibreELEC distro on. One of the guys even created an image for me with a specific kernel[1] (that I just upgraded the system with). [1] https://forum.libreelec.tv/thread/4235-dvb-issue-since-le-switched-to-kernel-4-9-x/?postID=77031#post77031 > My plan is to do more tests along this week, and try to tweak a little > bit both userspace and kernelspace, in order to see if I can get > better results. 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. Thus, if you manage to reproduce the case, try to see if adjusting this can mitigate the issue... Their system have non-preempt kernel, should they use PREEMPT? LibreELEC:~ # uname -a Linux LibreELEC 4.14.10 #1 SMP Tue Jan 9 17:35:03 GMT 2018 armv7l GNU/Linux [2] https://forum.libreelec.tv/thread/4235-dvb-issue-since-le-switched-to-kernel-4-9-x/?postID=76999#post76999
next prev parent reply other threads:[~2018-01-09 21:26 UTC|newest] Thread overview: 82+ 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> 2017-12-17 13:27 ` dvb usb issues since kernel 4.9 Mauro Carvalho Chehab [not found] ` <trinity-1fa14556-8596-44b1-95cb-b8919d94d2d4-1515251056328@3c-app-gmx-bs15> 2018-01-06 19:54 ` 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 2018-01-07 17:01 ` Aw: " Josef Griebichler 2018-01-07 17:01 ` Josef Griebichler 2018-01-08 9:43 ` Mauro Carvalho Chehab 2018-01-08 9:43 ` Mauro Carvalho Chehab 2018-01-08 16:10 ` Alan Stern 2018-01-08 16:10 ` Alan Stern 2018-01-08 16:26 ` Aw: " Josef Griebichler 2018-01-08 16:26 ` Josef Griebichler 2018-01-08 16:31 ` Alan Stern 2018-01-08 16:31 ` Alan Stern 2018-01-08 17:15 ` Aw: " Josef Griebichler 2018-01-08 17:15 ` Aw: " Josef Griebichler 2018-01-08 17:35 ` Aw: " Alan Stern 2018-01-08 17:35 ` Aw: " Alan Stern 2018-01-08 20:40 ` Jesper Dangaard Brouer 2018-01-08 20:40 ` Aw: " Jesper Dangaard Brouer 2018-01-08 21:31 ` Jesper Dangaard Brouer 2018-01-08 21:31 ` Aw: " Jesper Dangaard Brouer 2018-01-08 21:44 ` Peter Zijlstra 2018-01-08 21:44 ` Aw: " Peter Zijlstra 2018-01-08 22:16 ` Jesper Dangaard Brouer 2018-01-08 22:16 ` Aw: " Jesper Dangaard Brouer 2018-01-09 16:51 ` Josef Griebichler 2018-01-09 16:51 ` Josef Griebichler 2018-01-09 17:27 ` Eric Dumazet 2018-01-09 17:27 ` Aw: " Eric Dumazet 2018-01-09 17:48 ` Linus Torvalds 2018-01-09 17:48 ` Aw: " Linus Torvalds 2018-01-09 17:57 ` Eric Dumazet 2018-01-09 17:57 ` Aw: " Eric Dumazet 2018-01-09 18:58 ` Linus Torvalds 2018-01-09 18:58 ` Aw: " Linus Torvalds 2018-01-09 21:48 ` Eric Dumazet 2018-01-09 21:48 ` Aw: " Eric Dumazet 2018-01-10 9:45 ` Jesper Dangaard Brouer 2018-01-10 9:45 ` Aw: " Jesper Dangaard Brouer 2018-01-12 21:13 ` Mauro Carvalho Chehab 2018-01-12 21:13 ` Aw: " Mauro Carvalho Chehab 2018-01-12 21:48 ` Eric Dumazet 2018-01-12 21:48 ` Aw: " Eric Dumazet 2018-01-13 9:09 ` Mauro Carvalho Chehab 2018-01-13 9:09 ` Aw: " Mauro Carvalho Chehab 2018-01-13 10:46 ` Mauro Carvalho Chehab 2018-01-13 10:46 ` Aw: " 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 2018-01-08 19:51 ` Linus Torvalds 2018-01-09 17:42 ` Mauro Carvalho Chehab 2018-01-09 17:42 ` Mauro Carvalho Chehab 2018-01-09 17:55 ` Linus Torvalds 2018-01-09 17:55 ` Linus Torvalds 2018-01-09 21:26 ` Jesper Dangaard Brouer [this message] 2018-01-09 21:26 ` Jesper Dangaard Brouer 2018-01-10 3:02 ` Mike Galbraith 2018-01-10 3:02 ` Mike Galbraith 2018-07-17 11:54 ` Hanna Hawa 2018-07-17 11:54 ` hannah 2018-07-17 17:09 ` Linus Torvalds 2018-07-17 17:09 ` Linus Torvalds 2018-07-17 17:09 ` Linus Torvalds 2018-07-17 18:07 ` Hanna Hawa 2018-07-17 18:07 ` hannah 2018-07-17 18:07 ` Hanna Hawa 2018-07-17 22:21 ` Mauro Carvalho Chehab 2018-07-17 22:21 ` Mauro Carvalho Chehab 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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