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=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 AE2FEC43387 for ; Thu, 10 Jan 2019 16:30:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E7E3206B7 for ; Thu, 10 Jan 2019 16:30:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547137836; bh=Q4wBSFHlZ5JsYSF4PEc/HY6Lhy+R3VtJ+WOudiP0+yU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=JZz8Qm1nYZtDCCOKmfnwMMyCMwoTvd++TTp3DA9qmZhJZwqEfBHXkqON2GTIOFTOZ 82xq21BX72jNBX/ePlsBh/BXmzmhBVLvhbuz36pPuqZyo2mpnwdwerUfvfsYrglXxZ tOq8/Ko4zXI8MUqQmorDiUSW1MMG5ERutF/7eq44= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728127AbfAJQaf (ORCPT ); Thu, 10 Jan 2019 11:30:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:38158 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726242AbfAJQae (ORCPT ); Thu, 10 Jan 2019 11:30:34 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 41DB2206B7; Thu, 10 Jan 2019 16:30:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547137833; bh=Q4wBSFHlZ5JsYSF4PEc/HY6Lhy+R3VtJ+WOudiP0+yU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BLiN80RuZ/I6YnbT47rFgagiwYVljl7/DGZ5H1jcYU7R12HMzxvO6h6WKKyq3/nvs HIpYsLyrfaCioI9ODvSuiM6Jc9KHAj7hc4MVBZ0y82D+9BayT9EDhtWVMcYWvVGS7E HH6wZkIt2YioYBecaxYpfLygWtGFihaQG0tKCcSY= Date: Thu, 10 Jan 2019 17:30:30 +0100 From: Greg Kroah-Hartman To: Oleksij Rempel Cc: Linus Torvalds , Jiri Slaby , Pengutronix Kernel Team , lkml Subject: Re: [PATCH v1 3/3] drivers/tty: increase priority for tty_buffer_worker Message-ID: <20190110163030.GB19693@kroah.com> References: <20190110101232.9398-1-o.rempel@pengutronix.de> <20190110101232.9398-4-o.rempel@pengutronix.de> <20190110151953.qpat4t7lat6plfk6@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190110151953.qpat4t7lat6plfk6@pengutronix.de> User-Agent: Mutt/1.11.2 (2019-01-07) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 10, 2019 at 04:19:53PM +0100, Oleksij Rempel wrote: > > My gut feel is that if somebody still cares deeply about serial line > > latency, they should look at trying to see if they can do some of the > > work directly without the bounce to the workqueue. We use workqueues > > for a reason, but it's possible that some of it could be avoided at > > least in special cases... And yours sounds like a special case. > > It is for industrial low latency RS-422 based application. The loopback > test is just easy way to test/reproduce it without additional hardware. > > What is good, mainlineable way to implement it? What is the real problem your systems are having? Are they serial-port limited? Is latency a big issue? Trying to tune for a fake workload isn't the best way to solve anything :) thanks, greg k-h