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 73021C7EE29 for ; Tue, 13 Jun 2023 05:12:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239758AbjFMFMy (ORCPT ); Tue, 13 Jun 2023 01:12:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35582 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232951AbjFMFMu (ORCPT ); Tue, 13 Jun 2023 01:12:50 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F6EFE62; Mon, 12 Jun 2023 22:12:49 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 3C15261E69; Tue, 13 Jun 2023 05:12:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF78BC433EF; Tue, 13 Jun 2023 05:12:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686633168; bh=4kqAAS3SX9JNXmuGjywNhA17eJxvCECeHra6VxQaDBw=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=rbAhe7NZu5CJGvuBXPpPG9QRfEHcXU6mWWC3lAqUMgJzZksZaGuq9abalEXyNQYGq hwydWjeaSTHnGfeihlk8Kmug70g1h7hY7vlcCGy91OCznH28V746nwhAY8RT6HZxMp s2Pq9aTX4hi3DPFQBSnRlrM/x32KueeG78qNoPb5g7g/fplZXe+qnav5lGsE/IQMW9 Kd8/aDie78OS+g09yFMTWQNuNMUHjrAAh/wWl0mVa8mcXlJYb4M2yPxkhPYUM68Spd DONz2xi4bc1UsrQZ9oTFlgrGtdWdwj5bNqxIdfHHSSGfp+j00IZDGDJkv+xjyCKcaj svkSn+eGuYPTg== From: Kalle Valo To: Brian Norris Cc: Pin-yen Lin , Amitkumar Karwar , Ganapathi Bhat , Sharvari Harisangam , Xinming Hu , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] wifi: mwifiex: Replace RX workqueues with kthreads References: <20230609103651.313194-1-treapking@chromium.org> <87o7lohq9e.fsf@kernel.org> Date: Tue, 13 Jun 2023 08:12:42 +0300 In-Reply-To: (Brian Norris's message of "Mon, 12 Jun 2023 16:47:17 -0700") Message-ID: <87r0qgdjxx.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Brian Norris writes: > Hi, > > Thanks Pin-yen for most of the investigation here and for pushing the > patch. With some additional information though, I might suggest *not* > landing this patch at the moment. More details appended: > > On Sat, Jun 10, 2023 at 01:41:51AM +0800, Pin-yen Lin wrote: >> I realized that I might have over-simplified the background and the >> impact of this patch... >> >> The short answer to the question is that the throughput improved from >> 100 mbps to 180 mbps. The test was run on ChromeOS's v5.15 kernel >> fork. More detailed test setting is mentioned in [1]. >> >> However, the throughput of the same test case on our v4.19 kernel is >> 320 mbps. That is, we observed a 320 mbps --> 100 mbps regression when >> we tried to update the kernel version. This patch is more like a >> mitigation of the regression. It improves the throughput, even though >> it is still not as good as the older kernel. >> >> That being said, this patch does improve the throughput, so we think >> this patch can be landed into the mainline kernel. >> >> Best regards, >> Pin-yen >> >> [1]: https://lore.kernel.org/all/ZFvpJb9Dh0FCkLQA@google.com/ > > I (we?) was optimistic this would be an improvement (or at least, no > worse) due to some of the reasoning at [1]. And, the work here is just a > single work item, queued repeatedly to the same unbound workqueue. So > conceptually, it shouldn't be much different than a kthread_worker, > except for scheduler details -- where again, we'd think this should be > an improvement, as the scheduler would now better track load for the > task (mwifiex RX) in question. > > But additional testing on other mwifiex-based systems (RK3399 + PCIE > 8997) showed the inverse: some throughput drops on similar benchmarks, > from 110 Mbps to 80 Mbps. (Frankly, both numbers are significantly below > where we might like...) > > Considering we still don't have a full explanation for all the > performance differences we've been seeing (on either test platform), and > that at least one of our platforms showed a (smaller) regression, I > think we might want to do more research before committing to this. Yeah, I agree and I'll drop this. This is a really weird problem, I hope you can get to the bottom of it. -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches