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 140F4C31E49 for ; Thu, 13 Jun 2019 16:34:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E68BC20449 for ; Thu, 13 Jun 2019 16:34:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387898AbfFMQef (ORCPT ); Thu, 13 Jun 2019 12:34:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59370 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730767AbfFMHvS (ORCPT ); Thu, 13 Jun 2019 03:51:18 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C9D5230C0DEA; Thu, 13 Jun 2019 07:51:12 +0000 (UTC) Received: from localhost (ovpn-204-191.brq.redhat.com [10.40.204.191]) by smtp.corp.redhat.com (Postfix) with ESMTP id E4B86544FE; Thu, 13 Jun 2019 07:51:09 +0000 (UTC) Date: Thu, 13 Jun 2019 09:51:08 +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: <20190613075108.GA24650@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> <20190612125905.GB2600@redhat.com> <20190612142128.GA20760@redhat.com> <20190612144400.GB7016@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190612144400.GB7016@localhost.localdomain> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Thu, 13 Jun 2019 07:51:18 +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 04:44:01PM +0200, Lorenzo Bianconi wrote: > On Jun 12, Stanislaw Gruszka wrote: > > On Wed, Jun 12, 2019 at 02:59:05PM +0200, Stanislaw Gruszka wrote: > > > > > 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 . > > > > And if we could determine that there is no true need to use sg for rx, > > I think best approach here would be revert f8f527b16db5 in v5.2 to fix > > regression and remove rx sg in -next. That would make code simpler, > > allocate 4k instead 16k per packet, allow to use build_skb (4096 - 3839 > > give enough space for shared info) and not use usb hcd bounce buffer. > > I do not think we should drop sg support since: > - it allow us to rx huge amsdu frames (e.g. IEEE80211_MAX_MPDU_LEN_VHT_11454) > using multiple one page buffer. I think there will be new usb devices where we can > increase amsdu size (we can increase it even on mt76x2u usb 3.0 devices) I looked at intel wifi drivers and this is handled by amsdu_size module parameter, supported values are 4k, 8k and 12k. RX allocation size and proper values in vht_cap & ht_cap are set accordingly. Assuming (some) mt76 HW and FW can handle bigger AMSDUs I think we should do similar thing. Otherwise looks for me, we just waste memory and have not needed code for no true reason. > space needed for skb_shared_info is 320B on a x86_64 device Uhh, I haven't expected that sk_shared_info() is that big, so indeed build_skb could not used and 128B copy fallback will be necessary. Stanislaw