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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EAAA6C433F5 for ; Tue, 19 Oct 2021 15:52:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D562060EE3 for ; Tue, 19 Oct 2021 15:52:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233552AbhJSPy1 (ORCPT ); Tue, 19 Oct 2021 11:54:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:30969 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229803AbhJSPxr (ORCPT ); Tue, 19 Oct 2021 11:53:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1634658693; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=BzT6sYUvv1lM9/Iw/A1sGSgNrVx0j8X+NJF/dl2ARrg=; b=O3pi4SdqS5KwErkdDt/45HmpQg6dAyqEXHOYvvWoKQnj8UMSQYALqTB1euuc4HqUzDs00K NWFKa5wLJwlnFAZmuGc/AzBUi4vbp/4gIsK266Tlphas6mewtV+0x9EvhVtgNT7sPkiXLb OSus7oyPY0QKvBz4HDu+GBkBUdfE4Zg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-586-HcunPmxgO1CETEVleRbwPA-1; Tue, 19 Oct 2021 11:51:32 -0400 X-MC-Unique: HcunPmxgO1CETEVleRbwPA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 463E8879500; Tue, 19 Oct 2021 15:51:31 +0000 (UTC) Received: from fuller.cnet (ovpn-112-7.gru2.redhat.com [10.97.112.7]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9106D226E9; Tue, 19 Oct 2021 15:50:03 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id D4BD74149348; Tue, 19 Oct 2021 12:49:35 -0300 (-03) Message-ID: <20211019154210.739992013@fedora.localdomain> User-Agent: quilt/0.66 Date: Tue, 19 Oct 2021 12:24:34 -0300 From: Marcelo Tosatti To: linux-kernel@vger.kernel.org Cc: Nitesh Lal , Nicolas Saenz Julienne , Frederic Weisbecker , Christoph Lameter , Juri Lelli , Peter Zijlstra , Alex Belits , Peter Xu , Thomas Gleixner , Daniel Bristot de Oliveira , Marcelo Tosatti Subject: [patch v5 3/8] task isolation: sync vmstats on return to userspace References: <20211019152431.885037499@fedora.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The logic to disable vmstat worker thread, when entering nohz full, does not cover all scenarios. For example, it is possible for the following to happen: 1) enter nohz_full, which calls refresh_cpu_vm_stats, syncing the stats. 2) app runs mlock, which increases counters for mlock'ed pages. 3) start -RT loop Since refresh_cpu_vm_stats from nohz_full logic can happen _before_ the mlock, vmstat shepherd can restart vmstat worker thread on the CPU in question. To fix this, use the task isolation prctl interface to quiesce deferred actions when returning to userspace. Signed-off-by: Marcelo Tosatti --- v4: add oneshot mode support include/linux/task_isolation.h | 12 ++++++++++++ include/linux/vmstat.h | 8 ++++++++ kernel/entry/common.c | 2 ++ kernel/task_isolation.c | 22 ++++++++++++++++++++++ mm/vmstat.c | 21 +++++++++++++++++++++ 5 files changed, 65 insertions(+) Index: linux-2.6/include/linux/task_isolation.h =================================================================== --- linux-2.6.orig/include/linux/task_isolation.h +++ linux-2.6/include/linux/task_isolation.h @@ -40,8 +40,20 @@ int prctl_task_isolation_activate_set(un int __copy_task_isolation(struct task_struct *tsk); +void __isolation_exit_to_user_mode_prepare(void); + +static inline void isolation_exit_to_user_mode_prepare(void) +{ + if (current->isol_info) + __isolation_exit_to_user_mode_prepare(); +} + #else +static void isolation_exit_to_user_mode_prepare(void) +{ +} + static inline void tsk_isol_free(struct task_struct *tsk) { } Index: linux-2.6/include/linux/vmstat.h =================================================================== --- linux-2.6.orig/include/linux/vmstat.h +++ linux-2.6/include/linux/vmstat.h @@ -21,6 +21,14 @@ int sysctl_vm_numa_stat_handler(struct c void *buffer, size_t *length, loff_t *ppos); #endif +#ifdef CONFIG_SMP +void sync_vmstat(void); +#else +static inline void sync_vmstat(void) +{ +} +#endif + struct reclaim_stat { unsigned nr_dirty; unsigned nr_unqueued_dirty; Index: linux-2.6/kernel/entry/common.c =================================================================== --- linux-2.6.orig/kernel/entry/common.c +++ linux-2.6/kernel/entry/common.c @@ -6,6 +6,7 @@ #include #include #include +#include #include "common.h" @@ -285,6 +286,7 @@ static void syscall_exit_to_user_mode_pr static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs) { syscall_exit_to_user_mode_prepare(regs); + isolation_exit_to_user_mode_prepare(); local_irq_disable_exit_to_user(); exit_to_user_mode_prepare(regs); } Index: linux-2.6/kernel/task_isolation.c =================================================================== --- linux-2.6.orig/kernel/task_isolation.c +++ linux-2.6/kernel/task_isolation.c @@ -18,6 +18,8 @@ #include #include #include +#include +#include void __tsk_isol_free(struct task_struct *tsk) { @@ -355,3 +357,23 @@ int prctl_task_isolation_activate_get(un return ret; } +void __isolation_exit_to_user_mode_prepare(void) +{ + struct isol_info *i; + + i = current->isol_info; + if (!i) + return; + + if (i->active_mask != ISOL_F_QUIESCE) + return; + + if (i->quiesce_mask & ISOL_F_QUIESCE_VMSTATS) { + sync_vmstat(); + if (i->oneshot_mask & ISOL_F_QUIESCE_VMSTATS) { + i->oneshot_mask &= ~ISOL_F_QUIESCE_VMSTATS; + i->quiesce_mask &= ~ISOL_F_QUIESCE_VMSTATS; + } + } +} +EXPORT_SYMBOL_GPL(__isolation_exit_to_user_mode_prepare); Index: linux-2.6/mm/vmstat.c =================================================================== --- linux-2.6.orig/mm/vmstat.c +++ linux-2.6/mm/vmstat.c @@ -2003,6 +2003,27 @@ static void vmstat_shepherd(struct work_ round_jiffies_relative(sysctl_stat_interval)); } +void sync_vmstat(void) +{ + int cpu; + + cpu = get_cpu(); + + refresh_cpu_vm_stats(false); + put_cpu(); + + /* + * If task is migrated to another CPU between put_cpu + * and cancel_delayed_work_sync, the code below might + * cancel vmstat_update work for a different cpu + * (than the one from which the vmstats were flushed). + * + * However, vmstat shepherd will re-enable it later, + * so its harmless. + */ + cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu)); +} + static void __init start_shepherd_timer(void) { int cpu;