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=-12.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 083BBC433DF for ; Mon, 24 Aug 2020 05:20:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D3A26208E4 for ; Mon, 24 Aug 2020 05:20:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="vcT2u1US" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727944AbgHXFUm (ORCPT ); Mon, 24 Aug 2020 01:20:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725998AbgHXFUl (ORCPT ); Mon, 24 Aug 2020 01:20:41 -0400 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6E78C061573; Sun, 23 Aug 2020 22:20:41 -0700 (PDT) Received: by mail-pg1-x544.google.com with SMTP id d19so3997093pgl.10; Sun, 23 Aug 2020 22:20:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=a9FIkUYppAnd6RkZ+nRY1Ky5mZ+w/qdsOn9YUv8jqCk=; b=vcT2u1USQjCJsI84bF5cjPilghWnbfilgNMMkMOXcDM3+2zDyX7Lns15utnFh2rqfP VHaAlDe8TsZVVa++LzJtyzBwXew92XmzyNlNcqbsUnWPhANqxhbh2HpdPKLi/upCu8+5 ifADSYRQKXBCs03uXsBnmUjYdjh66TUE/EiEQgFHN7Knt9yygNqd3Jh9RxMzarGzDzrd iumBOYL4vGbiTAcz687oPEHbBouDdyUtKvjzcsaE+c7z4bePcfF1S4oLf1m45Q9bPIRv 4HRbS6jv6S50y3knrjSpKpsG+mqRPOn42sLY+ijVnMGByOfiAWQ2JdCnV7zL8Y06pmPw B9Mg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=a9FIkUYppAnd6RkZ+nRY1Ky5mZ+w/qdsOn9YUv8jqCk=; b=uWAh+dMtKrMpuDgTcFTA1M0CaxQs7leQypG6tZcxMkEa5VYH3/bWjsG9NcHkDGL08+ OzGp7FT6EhuxfGlr8BSLm8JgYDhq9JbXugblPe5Bib2JarLo306YzTsCjIgIY1sHMady hNfH3ga9GesoUsYSVXsMt2PG6Xz2MuFl9hNQ6mS4cXtUcVN1cdkoAeoXKboVjKCSTu9x 9fnvs7mgtL6mzsvfUAhooZ8Y1HhJtpEqF48rR4PyOm0mscU9vH0t24hKJPWyYtnL+aQV iECc9yYISjilFURizExnCzA1knODMKSd7D+/pe5IYe8A5BhPqNs5X4hsoG/6tG7/TEsB P04w== X-Gm-Message-State: AOAM533YbpLLJdzIxhhj8+2S909qfZjpbe5F6CPRP/EElA8chbPIPpsC EeUvyC718jt1v3Yqkq5WmMU= X-Google-Smtp-Source: ABdhPJwrhBJIL1QKHKD5mrhI0EjX1niAo/OIICj66vRZDhcyJOkkIdWNaYT3wCsw7VuN9syQevZA4A== X-Received: by 2002:aa7:9e4e:: with SMTP id z14mr3017901pfq.60.1598246441144; Sun, 23 Aug 2020 22:20:41 -0700 (PDT) Received: from localhost.localdomain ([103.7.29.9]) by smtp.gmail.com with ESMTPSA id r134sm9964167pfc.1.2020.08.23.22.20.38 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 23 Aug 2020 22:20:40 -0700 (PDT) From: Jiang Biao X-Google-Original-From: Jiang Biao To: bhelgaas@google.com Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Jiang Biao , Bin Lai Subject: [PATCH] driver/pci: reduce the single block time in pci_read_config Date: Mon, 24 Aug 2020 13:20:25 +0800 Message-Id: <20200824052025.48362-1-benbjiang@tencent.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jiang Biao pci_read_config() could block several ms in kernel space, mainly caused by the while loop to call pci_user_read_config_dword(). Singel pci_user_read_config_dword() loop could consume 130us+, | pci_user_read_config_dword() { | _raw_spin_lock_irq() { ! 136.698 us | native_queued_spin_lock_slowpath(); ! 137.582 us | } | pci_read() { | raw_pci_read() { | pci_conf1_read() { 0.230 us | _raw_spin_lock_irqsave(); 0.035 us | _raw_spin_unlock_irqrestore(); 8.476 us | } 8.790 us | } 9.091 us | } ! 147.263 us | } and dozens of the loop could consume ms+. If we execute some lspci commands concurrently, ms+ scheduling latency could be detected. Add scheduling chance in the loop to improve the latency. Reported-by: Bin Lai Signed-off-by: Jiang Biao --- drivers/pci/pci-sysfs.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 6d78df9..3b9f63d 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -708,6 +708,7 @@ static ssize_t pci_read_config(struct file *filp, struct kobject *kobj, data[off - init_off + 3] = (val >> 24) & 0xff; off += 4; size -= 4; + cond_resched(); } if (size >= 2) { -- 1.8.3.1