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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E0D4C61DA4 for ; Sat, 18 Feb 2023 12:05:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229481AbjBRMDJ convert rfc822-to-8bit (ORCPT ); Sat, 18 Feb 2023 07:03:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229441AbjBRMDJ (ORCPT ); Sat, 18 Feb 2023 07:03:09 -0500 Received: from lithops.sigma-star.at (lithops.sigma-star.at [195.201.40.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 26AB1A26C for ; Sat, 18 Feb 2023 04:03:06 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 9C06A642ECD2; Sat, 18 Feb 2023 13:03:04 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id GkhKrdvmyNYi; Sat, 18 Feb 2023 13:03:04 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 336F962EFEA2; Sat, 18 Feb 2023 13:03:04 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 9jg8mdLiCbiT; Sat, 18 Feb 2023 13:03:04 +0100 (CET) Received: from lithops.sigma-star.at (lithops.sigma-star.at [195.201.40.130]) by lithops.sigma-star.at (Postfix) with ESMTP id 1240D642ECD2; Sat, 18 Feb 2023 13:03:04 +0100 (CET) Date: Sat, 18 Feb 2023 13:03:03 +0100 (CET) From: Richard Weinberger To: wei fang Cc: Andrew Lunn , David Laight , netdev , shenwei wang , xiaoning wang , linux-imx Message-ID: <2030061857.147332.1676721783879.JavaMail.zimbra@nod.at> In-Reply-To: References: <1422776754.146013.1676652774408.JavaMail.zimbra@nod.at> <130183416.146934.1676713353800.JavaMail.zimbra@nod.at> Subject: Re: high latency with imx8mm compared to imx6q MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Originating-IP: [195.201.40.130] X-Mailer: Zimbra 8.8.12_GA_3807 (ZimbraWebClient - FF97 (Linux)/8.8.12_GA_3809) Thread-Topic: high latency with imx8mm compared to imx6q Thread-Index: KX6nItb3xzzXXgLsKrBE7F/dfPfNJbU33POAgABHTYCAAAZaMMtWSb1ctKpkzJDnhT13zw== Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org ----- Ursprüngliche Mail ----- > Von: "wei fang" >> Hm, I thought my settings are fine (IOW no coalescing at all). >> Coalesce parameters for eth0: >> Adaptive RX: n/a TX: n/a >> rx-usecs: 0 >> rx-frames: 0 >> tx-usecs: 0 >> tx-frames: 0 >> > Unfortunately, the fec driver does not support to set > rx-usecs/rx-frames/tx-usecs/tx-frames > to 0 to disable interrupt coalescing. 0 is an invalid parameters. :( So setting all values to 1 is the most "no coalescing" setting i can get? >> >> But I noticed something interesting this morning. When I set rx-usecs, tx-usecs, >> rx-frames and tx-frames to 1, *sometimes* the RTT is good. >> >> PING 192.168.0.52 (192.168.0.52) 56(84) bytes of data. >> 64 bytes from 192.168.0.52: icmp_seq=1 ttl=64 time=0.730 ms >> 64 bytes from 192.168.0.52: icmp_seq=2 ttl=64 time=0.356 ms >> 64 bytes from 192.168.0.52: icmp_seq=3 ttl=64 time=0.303 ms >> 64 bytes from 192.168.0.52: icmp_seq=4 ttl=64 time=2.22 ms >> 64 bytes from 192.168.0.52: icmp_seq=5 ttl=64 time=2.54 ms >> 64 bytes from 192.168.0.52: icmp_seq=6 ttl=64 time=0.354 ms >> 64 bytes from 192.168.0.52: icmp_seq=7 ttl=64 time=2.22 ms >> 64 bytes from 192.168.0.52: icmp_seq=8 ttl=64 time=2.54 ms >> 64 bytes from 192.168.0.52: icmp_seq=9 ttl=64 time=2.53 ms >> >> So coalescing plays a role but it looks like the ethernet controller does not >> always obey my settings. >> I didn't look into the configured registers so far, maybe ethtool does not set >> them correctly. >> > It look a bit weird. I did the same setting with my i.MX8ULP and didn't have > this > issue. I'm not sure whether you network is stable or network node devices also > enable interrupt coalescing and the relevant parameters are set to a bit high. I'm pretty sure my network is good, I've tested also different locations. And as I said, with the imx6q on the very same network everything works as expected. So, with rx-usecs/rx-frames/tx-usecs/tx-frames set to 1, you see a RTT smaller than 1ms? Thanks, //richard