From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from us-smtp-1.mimecast.com ([205.139.110.61] helo=us-smtp-delivery-1.mimecast.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iLSMO-0004Sb-B1 for ath10k@lists.infradead.org; Fri, 18 Oct 2019 13:32:06 +0000 Received: by mail-lj1-f197.google.com with SMTP id m8so1083946ljb.3 for ; Fri, 18 Oct 2019 06:31:59 -0700 (PDT) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= Subject: Re: [PATCH v2 1/4] mac80211: Rearrange ieee80211_tx_info to make room for tx_time_est In-Reply-To: <10b885b3238cede2d99c6134bebcc0c8ba6f6b10.camel@sipsolutions.net> References: <157115993755.2500430.12214017471129215800.stgit@toke.dk> <157115993866.2500430.13989567853855880476.stgit@toke.dk> <87sgnqe4wg.fsf@toke.dk> <10b885b3238cede2d99c6134bebcc0c8ba6f6b10.camel@sipsolutions.net> Date: Fri, 18 Oct 2019 15:31:56 +0200 Message-ID: <87imomdvsj.fsf@toke.dk> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "ath10k" Errors-To: ath10k-bounces+kvalo=adurom.com@lists.infradead.org To: Johannes Berg , Kan Yan Cc: Rajkumar Manoharan , Kevin Hayes , make-wifi-fast@lists.bufferbloat.net, linux-wireless@vger.kernel.org, ath10k@lists.infradead.org, John Crispin , Lorenzo Bianconi , Felix Fietkau Sm9oYW5uZXMgQmVyZyA8am9oYW5uZXNAc2lwc29sdXRpb25zLm5ldD4gd3JpdGVzOgoKPiBPbiBG cmksIDIwMTktMTAtMTggYXQgMTI6MTUgKzAyMDAsIFRva2UgSMO4aWxhbmQtSsO4cmdlbnNlbiB3 cm90ZToKPgo+PiBIb3dldmVyLCB0aGVyZSdzIGEgbmljZSBqdWljeSAndTE2IGFja19mcmFtZV9p ZCcgYXQgdGhlIHN0YXJ0IG9mCj4+IGllZWU4MDIxMV90eF9pbmZvLiBDb3VsZCB3ZSBwb3RlbnRp YWxseSB1c2UgdGhhdD8gV2UgY291bGQgdXNlIHRoZSB0b3AKPj4gYml0IGFzIGEgZGlzYW1iaWd1 YXRpb24gZmxhZzsgSSB0aGluayB3ZSdyZSBmaW5lIHdpdGggMTUgYml0cyBmb3IgdGhlIFRYCj4+ IHRpbWUgaXRzZWxmIChhIHNpbmdsZSBwYWNrZXQgd29uJ3QgZXhjZWVkIDhtcyBvciBUWCB0aW1l KSwgc28gaWYgd2UgY2FuCj4+IGxpdmUgd2l0aCAxNSBiaXRzIG9mIEFDSyBmcmFtZSBJRCBzcGFj ZSwgdGhhdCBjb3VsZCBiZSBhIHdheSBmb3J3YXJkPwo+Cj4gSSB3YXMgZ29pbmcgdG8gc2F5IHRo YXQgc2hvdWxkIHdvcmsgYXMgd2Ugb25seSBldmVyIGhhdmUgYSBoYW5kZnVsIG9mCj4gQUNLIGZy YW1lIElEcywgYnV0IC4uLiB5b3Ugc3RpbGwgbmVlZCB0aGUgYWlydGltZSBldmVuIGZvciBhIGZy YW1lIHRoYXQKPiB1c2Vyc3BhY2Ugd2FudHMgdG8ga25vdyB0aGUgQUNLIHN0YXR1cyBvZiwgbm8/ CgpPaCwgcmlnaHQuCgpXZWxsLCBsZXQncyB0cnkgdG8gZG8gdGhlIGFjdHVhbCBtYXRoLi4uIEEg ZnVsbC1zaXplICgxNTM4IGJ5dGVzKSBwYWNrZXQKdGFrZXMgfjIwNTAgbWljcm9zZWNvbmRzIHRv IHRyYW5zbWl0IGF0IDYgTWJwcy4gQWRkaW5nIGluIG92ZXJoZWFkLCBpdCdzCmNlcnRhaW5seSBz dGlsbCBsZXNzIHRoYXQgNDA5NiB1cywgc28gMTIgYml0cyBpcyBwbGVudHkuIFRoYXQgbGVhdmVz CmZvdXIgYml0cyBmb3IgdGhlIEFDSyBzdGF0dXMgSUQgaWYgd2UganVzdCBzcGxpdCB0aGUgdTE2 OyBpZiB3ZSBvbmx5CmV2ZXIgaGF2ZSAiYSBoYW5kZnVsIiwgdGhhdCBzaG91bGQgYmUgZW5vdWdo LCBubz8KCldlIGNvdWxkIGFsc28gc3BsaXQgNS8xMS4gVGhhdCB3b3VsZCBzdXBwb3J0IHVwIHRv IDMyIEFDSyBJRHMsIGFuZCB3ZQpjYW4ganVzdCB0cnVuY2F0ZSB0aGUgYWlydGltZSBhdCAyMDQ4 IHVzLCB3aGljaCBpcyBub3QgYSBiaWcgZGVhbCBJJ2QKc2F5LiBXZSBjb3VsZCBldmVuIHNwbGl0 IDYvMTAgYW5kIG9ubHkgbmVlZCB0byB0cnVuY2F0ZSB0aGUgVFggdGltZSBhdApyYXRlcyBiZWxv dyAxMyBNYnBzLi4uIE9yIHdlIGNvdWxkIHNhY3JpZmljZSBhIGJpdCB0byB0aGUgZmxhZyBhbmQg b25seQp0cnVuY2F0ZSBpZiB0aGUgQUNLIHN0YXR1cyBmbGFnIGlzIHNldC4KClRoaW5rIGl0IG1v c3RseSBkZXBlbmRzIG9uIHdoYXQgaXMgdGhlIHNtYWxsZXN0IElEIHNwYWNlIGZvciBBQ0sgSURz IHdlCmNhbiBsaXZlIHdpdGg/IDopCgotVG9rZQoKCl9fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fCmF0aDEwayBtYWlsaW5nIGxpc3QKYXRoMTBrQGxpc3RzLmlu ZnJhZGVhZC5vcmcKaHR0cDovL2xpc3RzLmluZnJhZGVhZC5vcmcvbWFpbG1hbi9saXN0aW5mby9h dGgxMGsK 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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 581E6CA9EA1 for ; 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[85.204.121.218]) by smtp.gmail.com with ESMTPSA id n17sm2124674ljc.44.2019.10.18.06.31.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Oct 2019 06:31:57 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 566B21804B6; Fri, 18 Oct 2019 15:31:56 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Johannes Berg , Kan Yan Cc: linux-wireless@vger.kernel.org, make-wifi-fast@lists.bufferbloat.net, ath10k@lists.infradead.org, John Crispin , Lorenzo Bianconi , Felix Fietkau , Rajkumar Manoharan , Kevin Hayes Subject: Re: [PATCH v2 1/4] mac80211: Rearrange ieee80211_tx_info to make room for tx_time_est In-Reply-To: <10b885b3238cede2d99c6134bebcc0c8ba6f6b10.camel@sipsolutions.net> References: <157115993755.2500430.12214017471129215800.stgit@toke.dk> <157115993866.2500430.13989567853855880476.stgit@toke.dk> <87sgnqe4wg.fsf@toke.dk> <10b885b3238cede2d99c6134bebcc0c8ba6f6b10.camel@sipsolutions.net> X-Clacks-Overhead: GNU Terry Pratchett Date: Fri, 18 Oct 2019 15:31:56 +0200 Message-ID: <87imomdvsj.fsf@toke.dk> MIME-Version: 1.0 X-MC-Unique: z_aKQ6mGNtGX_20ycYET0g-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org Johannes Berg writes: > On Fri, 2019-10-18 at 12:15 +0200, Toke H=C3=B8iland-J=C3=B8rgensen wrote= : > >> However, there's a nice juicy 'u16 ack_frame_id' at the start of >> ieee80211_tx_info. Could we potentially use that? We could use the top >> bit as a disambiguation flag; I think we're fine with 15 bits for the TX >> time itself (a single packet won't exceed 8ms or TX time), so if we can >> live with 15 bits of ACK frame ID space, that could be a way forward? > > I was going to say that should work as we only ever have a handful of > ACK frame IDs, but ... you still need the airtime even for a frame that > userspace wants to know the ACK status of, no? Oh, right. Well, let's try to do the actual math... A full-size (1538 bytes) packet takes ~2050 microseconds to transmit at 6 Mbps. Adding in overhead, it's certainly still less that 4096 us, so 12 bits is plenty. That leaves four bits for the ACK status ID if we just split the u16; if we only ever have "a handful", that should be enough, no? We could also split 5/11. That would support up to 32 ACK IDs, and we can just truncate the airtime at 2048 us, which is not a big deal I'd say. We could even split 6/10 and only need to truncate the TX time at rates below 13 Mbps... Or we could sacrifice a bit to the flag and only truncate if the ACK status flag is set. Think it mostly depends on what is the smallest ID space for ACK IDs we can live with? :) -Toke