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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 182D5C433E0 for ; Wed, 17 Jun 2020 11:11:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E63162078D for ; Wed, 17 Jun 2020 11:11:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WdVPNHXE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726326AbgFQLLN (ORCPT ); Wed, 17 Jun 2020 07:11:13 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:21652 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725536AbgFQLLM (ORCPT ); Wed, 17 Jun 2020 07:11:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592392270; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=syCj2SGtc29UR1l0pH8HnE/qBKvnb/ZgNc7oqht2v/k=; b=WdVPNHXEdf3NReG+vhjxldQSxIni1iaaB104eZ7Hq5DIrvtAMWV1n8VWXl/bDzT5g9gmGF yUQuRteO1QYxqDTJnTK6IWp/NkC4/i1K4dubTMUuDTJBXebizFi9xSym3MMRNrSNgc/uzk mgaLI06aqhFdum5uulKKQUMZDY1YRpY= 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-500-WYURySGxM-eei_-0bkmXEw-1; Wed, 17 Jun 2020 07:11:08 -0400 X-MC-Unique: WYURySGxM-eei_-0bkmXEw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A2D6A109132C; Wed, 17 Jun 2020 11:11:07 +0000 (UTC) Received: from gondolin (ovpn-112-222.ams2.redhat.com [10.36.112.222]) by smtp.corp.redhat.com (Postfix) with ESMTP id 84EE15D9D3; Wed, 17 Jun 2020 11:11:03 +0000 (UTC) Date: Wed, 17 Jun 2020 13:11:01 +0200 From: Cornelia Huck To: Christian Borntraeger Cc: David Hildenbrand , Janosch Frank , KVM , linux-s390 , Paolo Bonzini Subject: Re: [PATCH] KVM: s390: reduce number of IO pins to 1 Message-ID: <20200617131101.36d2475e.cohuck@redhat.com> In-Reply-To: <6953c580-9b99-1c76-b6eb-510dcb70894c@de.ibm.com> References: <20200617083620.5409-1-borntraeger@de.ibm.com> <6953c580-9b99-1c76-b6eb-510dcb70894c@de.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, 17 Jun 2020 13:04:52 +0200 Christian Borntraeger wrote: > On 17.06.20 12:19, David Hildenbrand wrote: > > On 17.06.20 10:36, Christian Borntraeger wrote: > >> The current number of KVM_IRQCHIP_NUM_PINS results in an order 3 > >> allocation (32kb) for each guest start/restart. This can result in OOM > >> killer activity even with free swap when the memory is fragmented > >> enough: > >> > >> kernel: qemu-system-s39 invoked oom-killer: gfp_mask=0x440dc0(GFP_KERNEL_ACCOUNT|__GFP_COMP|__GFP_ZERO), order=3, oom_score_adj=0 > >> kernel: CPU: 1 PID: 357274 Comm: qemu-system-s39 Kdump: loaded Not tainted 5.4.0-29-generic #33-Ubuntu > >> kernel: Hardware name: IBM 8562 T02 Z06 (LPAR) > >> kernel: Call Trace: > >> kernel: ([<00000001f848fe2a>] show_stack+0x7a/0xc0) > >> kernel: [<00000001f8d3437a>] dump_stack+0x8a/0xc0 > >> kernel: [<00000001f8687032>] dump_header+0x62/0x258 > >> kernel: [<00000001f8686122>] oom_kill_process+0x172/0x180 > >> kernel: [<00000001f8686abe>] out_of_memory+0xee/0x580 > >> kernel: [<00000001f86e66b8>] __alloc_pages_slowpath+0xd18/0xe90 > >> kernel: [<00000001f86e6ad4>] __alloc_pages_nodemask+0x2a4/0x320 > >> kernel: [<00000001f86b1ab4>] kmalloc_order+0x34/0xb0 > >> kernel: [<00000001f86b1b62>] kmalloc_order_trace+0x32/0xe0 > >> kernel: [<00000001f84bb806>] kvm_set_irq_routing+0xa6/0x2e0 > >> kernel: [<00000001f84c99a4>] kvm_arch_vm_ioctl+0x544/0x9e0 > >> kernel: [<00000001f84b8936>] kvm_vm_ioctl+0x396/0x760 > >> kernel: [<00000001f875df66>] do_vfs_ioctl+0x376/0x690 > >> kernel: [<00000001f875e304>] ksys_ioctl+0x84/0xb0 > >> kernel: [<00000001f875e39a>] __s390x_sys_ioctl+0x2a/0x40 > >> kernel: [<00000001f8d55424>] system_call+0xd8/0x2c8 > >> > >> As far as I can tell s390x does not use the iopins as we bail our for > >> anything other than KVM_IRQ_ROUTING_S390_ADAPTER and the chip/pin is > >> only used for KVM_IRQ_ROUTING_IRQCHIP. So let us use a small number to > >> reduce the memory footprint. > >> > >> Signed-off-by: Christian Borntraeger > >> --- > >> arch/s390/include/asm/kvm_host.h | 8 ++++---- > >> 1 file changed, 4 insertions(+), 4 deletions(-) > >> > >> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h > >> index cee3cb6455a2..6ea0820e7c7f 100644 > >> --- a/arch/s390/include/asm/kvm_host.h > >> +++ b/arch/s390/include/asm/kvm_host.h > >> @@ -31,12 +31,12 @@ > >> #define KVM_USER_MEM_SLOTS 32 > >> > >> /* > >> - * These seem to be used for allocating ->chip in the routing table, > >> - * which we don't use. 4096 is an out-of-thin-air value. If we need > >> - * to look at ->chip later on, we'll need to revisit this. > >> + * These seem to be used for allocating ->chip in the routing table, which we > >> + * don't use. 1 is as small as we can get to reduce the needed memory. If we > >> + * need to look at ->chip later on, we'll need to revisit this. > >> */ > >> #define KVM_NR_IRQCHIPS 1 > >> -#define KVM_IRQCHIP_NUM_PINS 4096 > >> +#define KVM_IRQCHIP_NUM_PINS 1 > >> #define KVM_HALT_POLL_NS_DEFAULT 50000 > >> > >> /* s390-specific vcpu->requests bit members */ > >> > > > > Guess it doesn't make sense to wrap all the "->chip" handling in a > > separate set of defines. > > > > Reviewed-by: David Hildenbrand > > I guess this is just the most simple solution. I am asking myself if I should add > cc stable of Fixes as I was able to trigger this by having several guests with a > reboot loop and several guests that trigger memory overcommitment. > Not sure if I would count this as a real bug -- it's mostly just that a large enough memory allocation may fail or draw the wrath of the oom killer. It still sucks; but I'm wondering why we trigger this after seven years.