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=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, PDS_TONAME_EQ_TOLOCAL_HDRS_LCASE,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 60914C433E0 for ; Tue, 9 Feb 2021 05:14:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F380E64EAC for ; Tue, 9 Feb 2021 05:14:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230156AbhBIFOJ (ORCPT ); Tue, 9 Feb 2021 00:14:09 -0500 Received: from kvm5.telegraphics.com.au ([98.124.60.144]:50874 "EHLO kvm5.telegraphics.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230244AbhBIFMV (ORCPT ); Tue, 9 Feb 2021 00:12:21 -0500 Received: from localhost (localhost.localdomain [127.0.0.1]) by kvm5.telegraphics.com.au (Postfix) with ESMTP id A65662B3DE; Tue, 9 Feb 2021 00:11:36 -0500 (EST) Date: Tue, 9 Feb 2021 16:11:40 +1100 (AEDT) From: Finn Thain To: tanxiaofei cc: jejb@linux.ibm.com, martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linuxarm@openeuler.org, linux-m68k@vger.kernel.org Subject: Re: [PATCH for-next 00/32] spin lock usage optimization for SCSI drivers In-Reply-To: Message-ID: References: <1612697823-8073-1-git-send-email-tanxiaofei@huawei.com> <31cd807d-3d0-ed64-60d-fde32cb3833c@telegraphics.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 9 Feb 2021, tanxiaofei wrote: > Hi Finn, > Thanks for reviewing the patch set. > > On 2021/2/8 15:57, Finn Thain wrote: > > On Sun, 7 Feb 2021, Xiaofei Tan wrote: > > > > > Replace spin_lock_irqsave with spin_lock in hard IRQ of SCSI drivers. > > > There are no function changes, but may speed up if interrupt happen too > > > often. > > > > This change doesn't necessarily work on platforms that support nested > > interrupts. > > > > Linux doesn't support nested interrupts anymore after the following > patch, so please don't worry this. > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e58aa3d2d0cc > Clearly that patch did not disable interrupts. It removed a statement that enabled them. > > Were you able to measure any benefit from this change on some other > > platform? > > > > It's hard to measure the benefit of this change. It's hard to see any benefit. But it's easy to see risk, when there's no indication that you've confirmed that the affected drivers do not rely on the irq lock, nor tested them for regressions, nor checked whether the affected platforms meet your assumuptions. > Hmm, you could take this patch set as cleanup. thanks. > A "cleanup" does not change program behaviour. Can you demonstrate that program behaviour is unchanged? > > Please see also, > > https://lore.kernel.org/linux-scsi/89c5cb05cb844939ae684db0077f675f@h3c.com/ > > > > . > > > >