From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-wm0-f43.google.com ([74.125.82.43]:38261 "EHLO mail-wm0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966037AbcKXPZO (ORCPT ); Thu, 24 Nov 2016 10:25:14 -0500 Date: Thu, 24 Nov 2016 16:25:11 +0100 From: Michal Hocko To: Johannes Berg Cc: LKML , linux-wireless Subject: Re: many "changed bandwidth, new config is" messages in the log Message-ID: <20161124152511.GC4776@dhcp22.suse.cz> (sfid-20161124_162524_926022_BF86839B) References: <20161124150723.GA4776@dhcp22.suse.cz> <1480000334.4388.2.camel@sipsolutions.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <1480000334.4388.2.camel@sipsolutions.net> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Thu 24-11-16 16:12:14, Johannes Berg wrote: > On Thu, 2016-11-24 at 15:07 +0000, Michal Hocko wrote: > > > I have only now managed to move to 4.9-rc5 (from 4.8) and started > > seeing quite a lot of following messages > > " > > [  346.612211] wlan0: AP c0:4a:00:f1:48:f2 changed bandwidth, new > > config is 2472 MHz, width 1 (2472/0 MHz) > > [  352.655929] wlan0: AP c0:4a:00:f1:48:f2 changed bandwidth, new > > config is 2472 MHz, width 2 (2462/0 MHz) > > " > > I don't think these messages are new in any way. checking ... nope, > it's been around that way since 3.9 :-) Right you are. I must have missed them before and git grep + git blame fooled me. > > It always seems to be changing width from 1 -> 2 and back > > Makes sense, that's 20 MHz <-> 40 MHz. > > Did you buy a new device that says it's 40 MHz incompatible or > something? I am using this device for years now. It is a cheap TP-Link home wireless router. So hard to tell about above. I am far from an expert. > Or perhaps one of your neighbors did ... Or something is > causing interference that makes the AP switch around. This might be possible. There are quite some devices broadcasting around $ sudo iwlist wlan0 scan | grep "Channel:" | sort | uniq -c 6 Channel:1 6 Channel:11 1 Channel:112 2 Channel:13 2 Channel:3 7 Channel:6 1 Channel:9 my router is at channel 13 so there seems to be something else sitting there as well. > > $ dmesg | grep "changed bandwidth" | wc -l > > 42 > > in 13 minutes of uptime. I have noticed this came in via 30eb1dc2c430 > > ("mac80211: properly track HT/VHT operation changes"). > > Right, but that went into 3.9 :-) > > > Is this something to be worried about? > > Not at all. I suppose we could make this a debug message though, it's > not super useful when it happens OK (sometimes it causes disconnections > when we can't support the new mode, which is more relevant). OK, I see. Then I would suggest lowering the loglevel ;) Thanks! -- Michal Hocko SUSE Labs