Return-path: Received: from mail-qc0-f178.google.com ([209.85.216.178]:58669 "EHLO mail-qc0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756133Ab3BRUK6 (ORCPT ); Mon, 18 Feb 2013 15:10:58 -0500 Message-ID: <51228ACF.3060500@lwfinger.net> (sfid-20130218_211113_804457_48B72F51) Date: Mon, 18 Feb 2013 14:10:55 -0600 From: Larry Finger MIME-Version: 1.0 To: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= CC: linville@tuxdriver.com, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, Bastian Bittorf , Stable Subject: Re: [PATCH] b43: Increase number of RX DMA slots References: <1361156480-32566-1-git-send-email-Larry.Finger@lwfinger.net> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 02/18/2013 10:18 AM, Rafał Miłecki wrote: > 2013/2/18 Larry Finger : >> Bastian Bittorf reported that some of the silent freezes on a Linksys WRT54G >> were due to overflow of the RX DMA ring buffer, which was created with 64 >> slots. That finding reminded me that I was seeing similar crashed on a netbook, >> which also has a relatively slow processor. After increasing the number of >> slots to 128, runs on the netbook that previously failed now worked; however, >> I found that 109 slots had been used in one test. For that reason, the number >> of slots is being increased to 256. > > So probably ideal solution is to use 128 *and* fix the driver's > failing on overflow ;) > > Did you try it on some old device? Just for sure firmware&DMA will > handle it correctly. I tested on BCM4318 (which is pretty old), and two different BCM4312 (14e4:4315) units. I think the firmware and DMA can handle it. After all, all the TX rings have 256 slots. There is, however, a question of the memory. TX only acquires the buffers when needed, but RX has to get them in advance, thus 256 slots there will waste a lot of memory. I agree that there be two patches, depending on Bastian's testing. The slot size change can be backported to stable. Larry