From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f54.google.com (mail-pa0-f54.google.com [209.85.220.54]) by kanga.kvack.org (Postfix) with ESMTP id 916756B0268 for ; Tue, 22 Dec 2015 16:55:23 -0500 (EST) Received: by mail-pa0-f54.google.com with SMTP id q3so102276311pav.3 for ; Tue, 22 Dec 2015 13:55:23 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id g65si14391556pfd.133.2015.12.22.13.55.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 22 Dec 2015 13:55:22 -0800 (PST) Date: Tue, 22 Dec 2015 13:55:20 -0800 From: Andrew Morton Subject: Re: [PATCH v2] memory-hotplug: add automatic onlining policy for the newly added memory Message-Id: <20151222135520.1bcb2d18382f1e414864992c@linux-foundation.org> In-Reply-To: <1450801950-7744-1-git-send-email-vkuznets@redhat.com> References: <1450801950-7744-1-git-send-email-vkuznets@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vitaly Kuznetsov Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, Jonathan Corbet , Greg Kroah-Hartman , Daniel Kiper , Dan Williams , Tang Chen , David Vrabel , David Rientjes , Naoya Horiguchi , Xishi Qiu , Mel Gorman , "K. Y. Srinivasan" , Igor Mammedov , Kay Sievers , Konrad Rzeszutek Wilk , Boris Ostrovsky On Tue, 22 Dec 2015 17:32:30 +0100 Vitaly Kuznetsov wrote: > Currently, all newly added memory blocks remain in 'offline' state unless > someone onlines them, some linux distributions carry special udev rules > like: > > SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", ATTR{state}="online" > > to make this happen automatically. This is not a great solution for virtual > machines where memory hotplug is being used to address high memory pressure > situations as such onlining is slow and a userspace process doing this > (udev) has a chance of being killed by the OOM killer as it will probably > require to allocate some memory. > > Introduce default policy for the newly added memory blocks in > /sys/devices/system/memory/hotplug_autoonline file with two possible > values: "offline" which preserves the current behavior and "online" which > causes all newly added memory blocks to go online as soon as they're added. > The default is "online" when MEMORY_HOTPLUG_AUTOONLINE kernel config option > is selected. I think the default should be "offline" so vendors can ship kernels which have CONFIG_MEMORY_HOTPLUG_AUTOONLINE=y while being back-compatible with previous kernels. > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2537,6 +2537,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > shutdown the other cpus. Instead use the REBOOT_VECTOR > irq. > > + nomemhp_autoonline Don't automatically online newly added memory. > + This wasn't mentioned in the changelog. Why do we need a boot parameter as well as the sysfs knob? > +config MEMORY_HOTPLUG_AUTOONLINE > + bool "Automatically online hot-added memory" > + depends on MEMORY_HOTPLUG_SPARSE > + help > + When memory is hot-added, it is not at ready-to-use state, a special "When memory is hot-added it is not in a ready-to-use state. A special" > + userspace action is required to online the newly added blocks. With > + this option enabled, the kernel will try to online all newly added > + memory automatically. > + > > ... > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org