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=-9.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 E4277C43441 for ; Wed, 14 Nov 2018 02:47:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AAAB62245E for ; Wed, 14 Nov 2018 02:47:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="dS+mW69T" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AAAB62245E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732699AbeKNMsJ (ORCPT ); Wed, 14 Nov 2018 07:48:09 -0500 Received: from mail.kernel.org ([198.145.29.99]:52082 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732434AbeKNMsH (ORCPT ); Wed, 14 Nov 2018 07:48:07 -0500 Received: from lerouge.suse.de (lfbn-ncy-1-241-207.w83-194.abo.wanadoo.fr [83.194.85.207]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A4F9522419; Wed, 14 Nov 2018 02:46:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1542163617; bh=eUj4RcSukekEPCJX4GbNOc6TawSt0YVnBhnGqU7g4fw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dS+mW69Td68Rv6GiaQNwsB0k4LI91bncHwUk9nx0GRyOgASpfA6KKD2KIFI3OrFVf CR33ZwBo5+wNyJFhYBwSTOJMF8IW7Wk8WDKUeK1NzxnrteGQ6vbdlML8anWGpzM3sa cXXpz+BEJTJ7U74XXmXwnmB2Gwe0rghX67rKJtPc= From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Peter Zijlstra , Wanpeng Li , Thomas Gleixner , Yauheni Kaliuta , Ingo Molnar , Rik van Riel Subject: [PATCH 18/25] vtime: Track nice-ness on top of context switch Date: Wed, 14 Nov 2018 03:46:02 +0100 Message-Id: <1542163569-20047-19-git-send-email-frederic@kernel.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1542163569-20047-1-git-send-email-frederic@kernel.org> References: <1542163569-20047-1-git-send-email-frederic@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We need to read the nice value of the task running on any CPU, possibly remotely, in order to correctly support kcpustat on nohz_full. Unfortunately we can't just read task_nice(tsk) when tsk runs on another CPU because its nice value may be concurrently changed. There could be a risk that a recently modified nice value is thought to apply for a longer while than is supposed to. For example if a task runs at T0 with nice = -10, then its nice value is changed at T0 + 1 second with nice = 10, a reader at T0 + 1 second could think that the task had this "nice == 10" value since the beginning (T0) and spuriously account 1 second nice time on kcpustat instead of 1 second user time. So we need to track the nice value changes under vtime seqcount. Start with context switches and account the vtime nice-ness on top of it. Signed-off-by: Frederic Weisbecker Cc: Yauheni Kaliuta Cc: Thomas Gleixner Cc: Rik van Riel Cc: Peter Zijlstra Cc: Wanpeng Li Cc: Ingo Molnar --- include/linux/sched.h | 1 + kernel/sched/cputime.c | 44 +++++++++++++++++++++++++++++++++++--------- 2 files changed, 36 insertions(+), 9 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 27e0544..356326f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -280,6 +280,7 @@ enum vtime_state { struct vtime { seqcount_t seqcount; unsigned long long starttime; + int nice; enum vtime_state state; unsigned int cpu; u64 utime; diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 8f5dee2..07c2e7f 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -735,13 +735,42 @@ static void vtime_account_system(struct task_struct *tsk, static void vtime_account_guest(struct task_struct *tsk, struct vtime *vtime) { + enum cpu_usage_stat index; + vtime->gtime += get_vtime_delta(vtime); - if (vtime->gtime >= TICK_NSEC) { - account_guest_time(tsk, vtime->gtime); - vtime->gtime = 0; - } + + if (vtime->gtime < TICK_NSEC) + return; + + if (vtime->nice) + index = CPUTIME_GUEST_NICE; + else + index = CPUTIME_GUEST; + + account_guest_time_index(tsk, vtime->gtime, index); + vtime->gtime = 0; } +static void vtime_account_user(struct task_struct *tsk, + struct vtime *vtime) +{ + enum cpu_usage_stat index; + + vtime->utime += get_vtime_delta(vtime); + + if (vtime->utime < TICK_NSEC) + return; + + if (vtime->nice) + index = CPUTIME_NICE; + else + index = CPUTIME_USER; + + account_user_time_index(tsk, vtime->utime, index); + vtime->utime = 0; +} + + static void __vtime_account_kernel(struct task_struct *tsk, struct vtime *vtime) { @@ -779,11 +808,7 @@ void vtime_user_exit(struct task_struct *tsk) struct vtime *vtime = &tsk->vtime; write_seqcount_begin(&vtime->seqcount); - vtime->utime += get_vtime_delta(vtime); - if (vtime->utime >= TICK_NSEC) { - account_user_time(tsk, vtime->utime); - vtime->utime = 0; - } + vtime_account_user(tsk, vtime); vtime->state = VTIME_SYS; write_seqcount_end(&vtime->seqcount); } @@ -864,6 +889,7 @@ void vtime_task_switch_generic(struct task_struct *prev) vtime->state = VTIME_SYS; vtime->starttime = sched_clock(); vtime->cpu = smp_processor_id(); + vtime->nice = (task_nice(current) > 0) ? 1 : 0; write_seqcount_end(&vtime->seqcount); rcu_assign_pointer(kcpustat->curr, current); -- 2.7.4