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=-14.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_IN_DEF_DKIM_WL 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 52184C433E1 for ; Tue, 23 Jun 2020 00:47:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 336542076E for ; Tue, 23 Jun 2020 00:47:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="YkuJYpxX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732312AbgFWArc (ORCPT ); Mon, 22 Jun 2020 20:47:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40474 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731716AbgFWArc (ORCPT ); Mon, 22 Jun 2020 20:47:32 -0400 Received: from mail-lj1-x242.google.com (mail-lj1-x242.google.com [IPv6:2a00:1450:4864:20::242]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D764C061573 for ; Mon, 22 Jun 2020 17:47:32 -0700 (PDT) Received: by mail-lj1-x242.google.com with SMTP id s9so1213471ljm.11 for ; Mon, 22 Jun 2020 17:47:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=wtdbOX5oThYTDJM/yZ7loxNE7l9NJR90MLvrHTPjroE=; b=YkuJYpxXvdEL7yoEauC9MJGL4fib0h9/hPyEoQNua/x651UUThCLvRj/xjLWmZU6UO YGPqNogOE8kx2yYabzpI88Lu955G6M0TmqFCJA0/Wl9BM870ahCsHhy4Ay2jWsvHxXPB MTDDLu5EniwwcBR4EvOhPuD/cRvMfy/EsS/avB8xiZHBWD6oI6JoZWSQP2DFX5hTuTXa 1ek7r8D77SmBHJ0rrl7FN9hWh874kcm4hBaC/maBiGUwlfLbGsQ3TqGTWRJtGw/jh/ik e04xUD5/povonUgqdwOL3arsqgMcTuITn93KR0jhV5JvYXIMmMygkFo9qhWslpOSKXjk 1LEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=wtdbOX5oThYTDJM/yZ7loxNE7l9NJR90MLvrHTPjroE=; b=TxiXB5geK0HxNQ4twzP+fT6tEq0N4/2qBdzcKKAPbMnyudbbRAt1dK1NzmwvAvl6nl e3AXFsMqmP1pCMNHm4HyCqV4XsEqAn27xQEcA4LKlyS8bPrRP5xagPB3Y+f7jcWWQza4 MrjQigCrkC3XQG83TtnGhlkpNO3ogRvxFv7xTN+7sU+00ziAGaVa4KqnLeqFO/vjPLoH q4aAoveR+YLr8aYhBNUwknV4hTkaOnx5KGTyL2eboKxogJLQVMxzbujDEcC8ACPbslWy ENFsVhIycwsMivGd9BwnLm3d7yHZ3kT3DIUVqrcMKLrwky9LTaB0FPAqbUmRMDjBsy04 JCag== X-Gm-Message-State: AOAM533YX6mnK2cYZ3qDylViOLUayB1LtefflyBpYVIE3xawe7eGliBX M97rOtgYzKt/OGqkxyYEuXew12SEE18pNqeDMsEgXw== X-Google-Smtp-Source: ABdhPJwd98jM9BRU2cXbE2BpTTuTTR91cyjV/GkqiL/DYfU/k2t4CLNN4nFu2jsYOQL7F3pAft5IhpPF7OzVZchP6R4= X-Received: by 2002:a2e:a58a:: with SMTP id m10mr10003481ljp.347.1592873250358; Mon, 22 Jun 2020 17:47:30 -0700 (PDT) MIME-Version: 1.0 References: <20200623002128.GA25456@paulmck-ThinkPad-P72> <20200623002147.25750-2-paulmck@kernel.org> In-Reply-To: <20200623002147.25750-2-paulmck@kernel.org> From: Shakeel Butt Date: Mon, 22 Jun 2020 17:47:19 -0700 Message-ID: Subject: Re: [PATCH tip/core/rcu 02/26] mm/mmap.c: Add cond_resched() for exit_mmap() CPU stalls To: paulmck@kernel.org, David Rientjes Cc: rcu@vger.kernel.org, LKML , Kernel Team , Ingo Molnar , jiangshanlai@gmail.com, dipankar@in.ibm.com, Andrew Morton , Mathieu Desnoyers , josh@joshtriplett.org, Thomas Gleixner , "Peter Zijlstra (Intel)" , Steven Rostedt , David Howells , Eric Dumazet , fweisbec@gmail.com, oleg@redhat.com, Joel Fernandes , Linux MM Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 22, 2020 at 5:22 PM wrote: > > From: "Paul E. McKenney" > > A large process running on a heavily loaded system can encounter the > following RCU CPU stall warning: > > rcu: INFO: rcu_sched self-detected stall on CPU > rcu: \x093-....: (20998 ticks this GP) idle=4ea/1/0x4000000000000002 softirq=556558/556558 fqs=5190 > \x09(t=21013 jiffies g=1005461 q=132576) > NMI backtrace for cpu 3 > CPU: 3 PID: 501900 Comm: aio-free-ring-w Kdump: loaded Not tainted 5.2.9-108_fbk12_rc3_3858_gb83b75af7909 #1 > Hardware name: Wiwynn HoneyBadger/PantherPlus, BIOS HBM6.71 02/03/2016 > Call Trace: > > dump_stack+0x46/0x60 > nmi_cpu_backtrace.cold.3+0x13/0x50 > ? lapic_can_unplug_cpu.cold.27+0x34/0x34 > nmi_trigger_cpumask_backtrace+0xba/0xca > rcu_dump_cpu_stacks+0x99/0xc7 > rcu_sched_clock_irq.cold.87+0x1aa/0x397 > ? tick_sched_do_timer+0x60/0x60 > update_process_times+0x28/0x60 > tick_sched_timer+0x37/0x70 > __hrtimer_run_queues+0xfe/0x270 > hrtimer_interrupt+0xf4/0x210 > smp_apic_timer_interrupt+0x5e/0x120 > apic_timer_interrupt+0xf/0x20 > > RIP: 0010:kmem_cache_free+0x223/0x300 > Code: 88 00 00 00 0f 85 ca 00 00 00 41 8b 55 18 31 f6 f7 da 41 f6 45 0a 02 40 0f 94 c6 83 c6 05 9c 41 5e fa e8 a0 a7 01 00 41 56 9d <49> 8b 47 08 a8 03 0f 85 87 00 00 00 65 48 ff 08 e9 3d fe ff ff 65 > RSP: 0018:ffffc9000e8e3da8 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13 > RAX: 0000000000020000 RBX: ffff88861b9de960 RCX: 0000000000000030 > RDX: fffffffffffe41e8 RSI: 000060777fe3a100 RDI: 000000000001be18 > RBP: ffffea00186e7780 R08: ffffffffffffffff R09: ffffffffffffffff > R10: ffff88861b9dea28 R11: ffff88887ffde000 R12: ffffffff81230a1f > R13: ffff888854684dc0 R14: 0000000000000206 R15: ffff8888547dbc00 > ? remove_vma+0x4f/0x60 > remove_vma+0x4f/0x60 > exit_mmap+0xd6/0x160 > mmput+0x4a/0x110 > do_exit+0x278/0xae0 > ? syscall_trace_enter+0x1d3/0x2b0 > ? handle_mm_fault+0xaa/0x1c0 > do_group_exit+0x3a/0xa0 > __x64_sys_exit_group+0x14/0x20 > do_syscall_64+0x42/0x100 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > And on a PREEMPT=n kernel, the "while (vma)" loop in exit_mmap() can run > for a very long time given a large process. This commit therefore adds > a cond_resched() to this loop, providing RCU any needed quiescent states. > > Cc: Andrew Morton > Cc: > Signed-off-by: Paul E. McKenney We have exactly the same change in our internal kernel since 2018. We mostly observed the need_resched warnings on the processes mapping the hugetlbfs. Reviewed-by: Shakeel Butt > --- > mm/mmap.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 59a4682..972f839 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -3159,6 +3159,7 @@ void exit_mmap(struct mm_struct *mm) > if (vma->vm_flags & VM_ACCOUNT) > nr_accounted += vma_pages(vma); > vma = remove_vma(vma); > + cond_resched(); > } > vm_unacct_memory(nr_accounted); > } > -- > 2.9.5 > 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=-14.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_IN_DEF_DKIM_WL 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 D4E7BC433E0 for ; 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Mon, 22 Jun 2020 17:47:30 -0700 (PDT) MIME-Version: 1.0 References: <20200623002128.GA25456@paulmck-ThinkPad-P72> <20200623002147.25750-2-paulmck@kernel.org> In-Reply-To: <20200623002147.25750-2-paulmck@kernel.org> From: Shakeel Butt Date: Mon, 22 Jun 2020 17:47:19 -0700 Message-ID: Subject: Re: [PATCH tip/core/rcu 02/26] mm/mmap.c: Add cond_resched() for exit_mmap() CPU stalls To: paulmck@kernel.org, David Rientjes Cc: rcu@vger.kernel.org, LKML , Kernel Team , Ingo Molnar , jiangshanlai@gmail.com, dipankar@in.ibm.com, Andrew Morton , Mathieu Desnoyers , josh@joshtriplett.org, Thomas Gleixner , "Peter Zijlstra (Intel)" , Steven Rostedt , David Howells , Eric Dumazet , fweisbec@gmail.com, oleg@redhat.com, Joel Fernandes , Linux MM Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 85729180326C6 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jun 22, 2020 at 5:22 PM wrote: > > From: "Paul E. McKenney" > > A large process running on a heavily loaded system can encounter the > following RCU CPU stall warning: > > rcu: INFO: rcu_sched self-detected stall on CPU > rcu: \x093-....: (20998 ticks this GP) idle=4ea/1/0x4000000000000002 softirq=556558/556558 fqs=5190 > \x09(t=21013 jiffies g=1005461 q=132576) > NMI backtrace for cpu 3 > CPU: 3 PID: 501900 Comm: aio-free-ring-w Kdump: loaded Not tainted 5.2.9-108_fbk12_rc3_3858_gb83b75af7909 #1 > Hardware name: Wiwynn HoneyBadger/PantherPlus, BIOS HBM6.71 02/03/2016 > Call Trace: > > dump_stack+0x46/0x60 > nmi_cpu_backtrace.cold.3+0x13/0x50 > ? lapic_can_unplug_cpu.cold.27+0x34/0x34 > nmi_trigger_cpumask_backtrace+0xba/0xca > rcu_dump_cpu_stacks+0x99/0xc7 > rcu_sched_clock_irq.cold.87+0x1aa/0x397 > ? tick_sched_do_timer+0x60/0x60 > update_process_times+0x28/0x60 > tick_sched_timer+0x37/0x70 > __hrtimer_run_queues+0xfe/0x270 > hrtimer_interrupt+0xf4/0x210 > smp_apic_timer_interrupt+0x5e/0x120 > apic_timer_interrupt+0xf/0x20 > > RIP: 0010:kmem_cache_free+0x223/0x300 > Code: 88 00 00 00 0f 85 ca 00 00 00 41 8b 55 18 31 f6 f7 da 41 f6 45 0a 02 40 0f 94 c6 83 c6 05 9c 41 5e fa e8 a0 a7 01 00 41 56 9d <49> 8b 47 08 a8 03 0f 85 87 00 00 00 65 48 ff 08 e9 3d fe ff ff 65 > RSP: 0018:ffffc9000e8e3da8 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13 > RAX: 0000000000020000 RBX: ffff88861b9de960 RCX: 0000000000000030 > RDX: fffffffffffe41e8 RSI: 000060777fe3a100 RDI: 000000000001be18 > RBP: ffffea00186e7780 R08: ffffffffffffffff R09: ffffffffffffffff > R10: ffff88861b9dea28 R11: ffff88887ffde000 R12: ffffffff81230a1f > R13: ffff888854684dc0 R14: 0000000000000206 R15: ffff8888547dbc00 > ? remove_vma+0x4f/0x60 > remove_vma+0x4f/0x60 > exit_mmap+0xd6/0x160 > mmput+0x4a/0x110 > do_exit+0x278/0xae0 > ? syscall_trace_enter+0x1d3/0x2b0 > ? handle_mm_fault+0xaa/0x1c0 > do_group_exit+0x3a/0xa0 > __x64_sys_exit_group+0x14/0x20 > do_syscall_64+0x42/0x100 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > And on a PREEMPT=n kernel, the "while (vma)" loop in exit_mmap() can run > for a very long time given a large process. This commit therefore adds > a cond_resched() to this loop, providing RCU any needed quiescent states. > > Cc: Andrew Morton > Cc: > Signed-off-by: Paul E. McKenney We have exactly the same change in our internal kernel since 2018. We mostly observed the need_resched warnings on the processes mapping the hugetlbfs. Reviewed-by: Shakeel Butt > --- > mm/mmap.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 59a4682..972f839 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -3159,6 +3159,7 @@ void exit_mmap(struct mm_struct *mm) > if (vma->vm_flags & VM_ACCOUNT) > nr_accounted += vma_pages(vma); > vma = remove_vma(vma); > + cond_resched(); > } > vm_unacct_memory(nr_accounted); > } > -- > 2.9.5 >