From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96668C31E46 for ; Wed, 12 Jun 2019 12:59:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 77C4120866 for ; Wed, 12 Jun 2019 12:59:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2439235AbfFLM7L (ORCPT ); Wed, 12 Jun 2019 08:59:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32658 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2437214AbfFLM7L (ORCPT ); Wed, 12 Jun 2019 08:59:11 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E9BBF356D3; Wed, 12 Jun 2019 12:59:10 +0000 (UTC) Received: from localhost (unknown [10.43.2.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8FD2068431; Wed, 12 Jun 2019 12:59:08 +0000 (UTC) Date: Wed, 12 Jun 2019 14:59:06 +0200 From: Stanislaw Gruszka To: Lorenzo Bianconi Cc: Lorenzo Bianconi , nbd@nbd.name, kvalo@codeaurora.org, linux-wireless@vger.kernel.org Subject: Re: [PATCH v2 2/2] mt76: usb: do not always copy the first part of received frames Message-ID: <20190612125905.GB2600@redhat.com> References: <2ed0b595a12944a8cfea14e066bcc4fa24f0ba44.1559293385.git.lorenzo@kernel.org> <20190612091036.GB2965@redhat.com> <20190612095302.GD8107@localhost.localdomain> <20190612102502.GB4431@redhat.com> <20190612104921.GF8107@localhost.localdomain> <20190612115120.GA3496@redhat.com> <20190612122845.GH8107@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190612122845.GH8107@localhost.localdomain> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 12 Jun 2019 12:59:11 +0000 (UTC) Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Wed, Jun 12, 2019 at 02:28:48PM +0200, Lorenzo Bianconi wrote: > [...] > > > > My sense of humor declined quite drastically lastly ;-/ > > > > > > > but we can be more cautious since probably copying > > > > > the first 128B will not make any difference > > > > > > > > Not sure if I understand what you mean. > > > > > > Please correct me if I am wrong but I think max amsdu rx size is 3839B for > > > mt76. For the sg_en case this frame will span over multiple sg buffers since > > > sg buffer size is 2048B (2 sg buffers). Moreover if we do not take into account > > > skb_shared_info when configuring the sg buffer size we will need to always copy > > > the first 128B of the first buffer since received len will be set to 2048 and > > > the following if condition will always fail: > > > > > > if (SKB_WITH_OVERHEAD(buf_size) >= MT_DMA_HDR_LEN + len) { > > > } > > > > Ok, that I understand. > > > > > > > > And skb_shered_info is needed only in first buffer IIUC. > > > > > > > > > > > > Also this patch seems to make first patch unnecessary except for > > > > > > non sg_en case (in which I think rx AMSDU is broken anyway), > > > > > > so I would prefer just to apply first patch. > > > > > > > > > > I do not think rx AMSDU is broken for non sg_en case since the max rx value > > > > > allowed should be 3839 IIRC and we alloc one page in this case > > > > > > > > If that's the case we should be fine, but then I do not understand > > > > why we allocate 8*2k buffers for sg_en case, isn't that AP can > > > > sent AMSDU frame 16k big? > > > > > > Sorry I did not get what you mean here, could you please explain? > > > > If max RX AMSDU size is 3839B I do not see reason why we allocate > > MT_SG_MAX_SIZE=8 of MT_RX_BUF_SIZE=2k buffers for sg_en case. > > I thought the reason is that max AMSDU size is 16kB so it fit into > > 8 sg buffers of 2k. > > > > In other words, for me, looks like either > > - we can not handle AMSDU for non sg case because we do not > > allocate big enough buffer > > I think AMSDU is mandatory and we currently support it even for non-sg case > (since max rx AMSDU is 3839B) > > > or > > - we can just use one PAGE_SIZE buffer for rx and remove sg > > buffers for rx completely > > using sg buffers we can support bigger rx AMSDU size in the future without using > huge buffers (e.g. we can try to use IEEE80211_MAX_MPDU_LEN_HT_7935 with > mt76x2u) I think it would be simpler just to allocate 2 pages for 7935B . Stanislaw