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=-5.8 required=3.0 tests=BAYES_00,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 60DDAC4361B for ; Tue, 8 Dec 2020 13:14:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 12C2223AA8 for ; Tue, 8 Dec 2020 13:14:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725931AbgLHNOB (ORCPT ); Tue, 8 Dec 2020 08:14:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54044 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725881AbgLHNOB (ORCPT ); Tue, 8 Dec 2020 08:14:01 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 130E8C061749 for ; Tue, 8 Dec 2020 05:13:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=mwUwAz4oo7DdtTjCJXSgglhbE80qb3YirGBlxjlaxWQ=; b=Fy7ri/MSQxKRAV5VsOcE+VAGGK zn6yBWK9ecErdjd6F0djhf+KZ6FvOFHjx1wvtJkwDkClQ7v51QsPb/GWAM0u5ZcD549EU9v/MCwa1 Oiy3WRj0JgoO4F6Sh7Hqsz2roLJP5Pi8DzEZQ6NjSPMhQglJc8aUpPj+kYNqGkwQvTTVev/elS0/V 4kzxbhqUmy27k2DJIj++G0INYKZG76bNRWKjq76gA5wDT8eo9Se0y8wd7KCWO+cOT16JXK8W3geVr ZCG2kU3X4mKh1IPLpXNSNvZu8OKv1FMZKw8owil/DJWmyvxu46c0L7NkLDO8Nmh7aInvubteA/Xhi K/44dgWQ==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kmcnv-0005zJ-4N; Tue, 08 Dec 2020 13:13:19 +0000 Date: Tue, 8 Dec 2020 13:13:19 +0000 From: Christoph Hellwig To: Jens Axboe Cc: Sebastian Andrzej Siewior , linux-block@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , Daniel Wagner , Mike Galbraith , Christoph Hellwig , Sagi Grimberg Subject: Re: [PATCH 2/3] blk-mq: Always complete remote completions requests in softirq Message-ID: <20201208131319.GB22219@infradead.org> References: <20201204191356.2516405-1-bigeasy@linutronix.de> <20201204191356.2516405-3-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Dec 07, 2020 at 04:52:57PM -0700, Jens Axboe wrote: > On 12/4/20 12:13 PM, Sebastian Andrzej Siewior wrote: > > Controllers with multiple queues have their IRQ-handelers pinned to a > > CPU. The core shouldn't need to complete the request on a remote CPU. > > > > Remove this case and always raise the softirq to complete the request. > > I don't like this one at all, it'll add a softirq jump for the fast path > for eg nvme devices. For the real fast path, that is either a polled queue or irq driven queues that only map to a single CPU we are never reaching this code, so I'm not too worried. Not that I'd complain about numbers, preferably in the commit log.