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 BB7B4C31E45 for ; Thu, 13 Jun 2019 15:53:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 94E1820851 for ; Thu, 13 Jun 2019 15:53:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731618AbfFMPxS (ORCPT ); Thu, 13 Jun 2019 11:53:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56772 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731619AbfFMJDm (ORCPT ); Thu, 13 Jun 2019 05:03:42 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 510373172D64; Thu, 13 Jun 2019 09:03:37 +0000 (UTC) Received: from localhost (unknown [10.43.2.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9F9885F9B0; Thu, 13 Jun 2019 09:03:33 +0000 (UTC) Date: Thu, 13 Jun 2019 11:02:02 +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: <20190613090201.GA2753@redhat.com> References: <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> <20190613075108.GA24650@redhat.com> <20190613082637.GA18296@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190613082637.GA18296@localhost.localdomain> User-Agent: Mutt/1.5.20 (2009-12-10) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Thu, 13 Jun 2019 09:03:42 +0000 (UTC) Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org Hi On Thu, Jun 13, 2019 at 10:26:38AM +0200, Lorenzo Bianconi wrote: > [...] > > > 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. > > Hi Stanislaw, > > reviewing the original patch I think we can't trigger any IOMMU bug since the > usb buffer length is actually 2048 and not 2048 + skb_shared_info_size: I'm concerned about alignment and crossing pages boundaries. If you allocate via page_frag_alloc() buffers, except first one, will have 'not natural' alignment and every second will be spanned across two pages. Stanislaw