From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: dvb usb issues since kernel 4.9 From: Jesper Dangaard Brouer Message-Id: <20180109222604.64d4377c@redhat.com> Date: Tue, 9 Jan 2018 22:26:04 +0100 To: Mauro Carvalho Chehab Cc: Linus Torvalds , Peter Zijlstra , Alan Stern , Ingo Molnar , Josef Griebichler , Greg Kroah-Hartman , USB list , Eric Dumazet , Rik van Riel , Paolo Abeni , Hannes Frederic Sowa , linux-kernel , netdev , Jonathan Corbet , LMML , David Miller List-ID: T24gVHVlLCA5IEphbiAyMDE4IDE1OjQyOjM1IC0wMjAwIE1hdXJvIENhcnZhbGhvIENoZWhhYiA8 bWNoZWhhYkBzLW9wZW5zb3VyY2UuY29tPiB3cm90ZToKPiBFbSBNb24sIDggSmFuIDIwMTggMTE6 NTE6MDQgLTA4MDAgTGludXMgVG9ydmFsZHMgPHRvcnZhbGRzQGxpbnV4LWZvdW5kYXRpb24ub3Jn PiBlc2NyZXZldToKPiAKWy4uLl0KPiBQYXRjaCBtYWtlcyBzZW5zZSB0byBtZSwgYWx0aG91Z2gg SSB3YXMgbm90IGFibGUgdG8gdGVzdCBpdCBteXNlbGYuCiAKVGhlIHBhdGNoIGFsc28gbWFrZSBz ZW5zZSB0byBtZS4gIEkndmUgZG9uZSBzb21lIGJhc2ljIHRlc3Rpbmcgd2l0aCBpdApvbiBteSBo aWdoLWVuZCBCcm9hZHdlbGwgc3lzdGVtICh0aGF0IEkgdXNlIGZvciAxMDBHYml0L3MgdGVzdGlu ZykuIEFzCmV4cGVjdGVkIHRoZSBuZXR3b3JrIG92ZXJsb2FkIGNhc2Ugc3RpbGwgd29ya3MsIGFz IE5FVF9SWF9TT0ZUSVJRIGlzCm5vdCBtYXRjaGVkLiAKCj4gSSBzZXQgYSBSUGkzIG1hY2hpbmUg aGVyZSB3aXRoIHZhbmlsbGEgS2VybmVsIDQuMTQuMTEgcnVubmluZyBhCj4gc3RhbmRhcmQgcmFz cGJpYW4gZGlzdHJpYnV0aW9uICh3aXRoIGVsZXZhdG9yPWRlYWRsaW5lKS4KCkkgZm91bmQgYSBS YXNwYmVycnkgUGkgTW9kZWwgQisgKEkgdGhpbmssIEJDTTI4MzUpLCB0aGF0IEkgbG9hZGVkIHRo ZQpMaWJyZUVMRUMgZGlzdHJvIG9uLiAgT25lIG9mIHRoZSBndXlzIGV2ZW4gY3JlYXRlZCBhbiBp bWFnZSBmb3IgbWUgd2l0aAphIHNwZWNpZmljIGtlcm5lbFsxXSAodGhhdCBJIGp1c3QgdXBncmFk ZWQgdGhlIHN5c3RlbSB3aXRoKS4KClsxXSBodHRwczovL2ZvcnVtLmxpYnJlZWxlYy50di90aHJl YWQvNDIzNS1kdmItaXNzdWUtc2luY2UtbGUtc3dpdGNoZWQtdG8ta2VybmVsLTQtOS14Lz9wb3N0 SUQ9NzcwMzEjcG9zdDc3MDMxCiAKPiBNeSBwbGFuIGlzIHRvIGRvIG1vcmUgdGVzdHMgYWxvbmcg dGhpcyB3ZWVrLCBhbmQgdHJ5IHRvIHR3ZWFrIGEgbGl0dGxlCj4gYml0IGJvdGggdXNlcnNwYWNl IGFuZCBrZXJuZWxzcGFjZSwgaW4gb3JkZXIgdG8gc2VlIGlmIEkgY2FuIGdldAo+IGJldHRlciBy ZXN1bHRzLgogCkkndmUgcHJldmlvdXNseSBleHBlcmllbmNlZCB0aGF0IHlvdSBjYW4gYmUgYWZm ZWN0ZWQgYnkgdGhlIHNjaGVkdWxlcgpncmFudWxhcml0eSwgd2hpY2ggaXMgYWRqdXN0YWJsZSAo d2l0aCBDT05GSUdfU0NIRURfREVCVUc9eSk6CgogJCBncmVwIC1IIC4gL3Byb2Mvc3lzL2tlcm5l bC9zY2hlZF8qX2dyYW51bGFyaXR5X25zCiAvcHJvYy9zeXMva2VybmVsL3NjaGVkX21pbl9ncmFu dWxhcml0eV9uczoyMjUwMDAwCiAvcHJvYy9zeXMva2VybmVsL3NjaGVkX3dha2V1cF9ncmFudWxh cml0eV9uczozMDAwMDAwCgpUaGUgYWJvdmUgbnVtYmVycyB3ZXJlIGNvbmZpcm1lZCBvbiB0aGUg UlBpMiAoc2VlWzJdKS4gV2l0aCBjb21taXQKNGNkMTNjMjFiMjA3ICgic29mdGlycTogTGV0IGtz b2Z0aXJxZCBkbyBpdHMgam9iIiksIEkgZXhwZWN0L2Fzc3VtZSB0aGF0CnNvZnRpcnEgcHJvY2Vz c2luZyBsYXRlbmN5IGlzIGJvdW5kZWQgYnkgdGhlIHNjaGVkX3dha2V1cF9ncmFudWxhcml0eV9u cywKd2hpY2ggd2l0aCAzIG1zIGlzIG5vdCBnb29kIGVub3VnaCBmb3IgdGhlaXIgdXNlLWNhc2Uu CgpUaHVzLCBpZiB5b3UgbWFuYWdlIHRvIHJlcHJvZHVjZSB0aGUgY2FzZSwgdHJ5IHRvIHNlZSBp ZiBhZGp1c3RpbmcgdGhpcwpjYW4gbWl0aWdhdGUgdGhlIGlzc3VlLi4uCgoKVGhlaXIgc3lzdGVt IGhhdmUgbm9uLXByZWVtcHQga2VybmVsLCBzaG91bGQgdGhleSB1c2UgUFJFRU1QVD8KCiBMaWJy ZUVMRUM6fiAjIHVuYW1lIC1hCiBMaW51eCBMaWJyZUVMRUMgNC4xNC4xMCAjMSBTTVAgVHVlIEph biA5IDE3OjM1OjAzIEdNVCAyMDE4IGFybXY3bCBHTlUvTGludXgKClsyXSBodHRwczovL2ZvcnVt LmxpYnJlZWxlYy50di90aHJlYWQvNDIzNS1kdmItaXNzdWUtc2luY2UtbGUtc3dpdGNoZWQtdG8t a2VybmVsLTQtOS14Lz9wb3N0SUQ9NzY5OTkjcG9zdDc2OTk5Cg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]:47184 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751749AbeAIV0V (ORCPT ); Tue, 9 Jan 2018 16:26:21 -0500 Date: Tue, 9 Jan 2018 22:26:04 +0100 From: Jesper Dangaard Brouer To: Mauro Carvalho Chehab Cc: Linus Torvalds , Peter Zijlstra , Alan Stern , Ingo Molnar , Josef Griebichler , Greg Kroah-Hartman , USB list , Eric Dumazet , Rik van Riel , Paolo Abeni , Hannes Frederic Sowa , linux-kernel , netdev , Jonathan Corbet , LMML , David Miller Subject: Re: dvb usb issues since kernel 4.9 Message-ID: <20180109222604.64d4377c@redhat.com> In-Reply-To: <20180109154235.2a42f0a0@vento.lan> References: <20180109154235.2a42f0a0@vento.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On Tue, 9 Jan 2018 15:42:35 -0200 Mauro Carvalho Chehab wrote: > Em Mon, 8 Jan 2018 11:51:04 -0800 Linus Torvalds 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