From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id BD3AB82F64 for ; Tue, 22 Dec 2015 17:26:06 -0500 (EST) Received: by mail-pa0-f53.google.com with SMTP id cy9so40967412pac.0 for ; Tue, 22 Dec 2015 14:26:06 -0800 (PST) Received: from mail-pf0-x22b.google.com (mail-pf0-x22b.google.com. [2607:f8b0:400e:c00::22b]) by mx.google.com with ESMTPS id e21si14429768pfb.51.2015.12.22.14.26.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 22 Dec 2015 14:26:06 -0800 (PST) Received: by mail-pf0-x22b.google.com with SMTP id q63so6570227pfb.0 for ; Tue, 22 Dec 2015 14:26:06 -0800 (PST) Date: Tue, 22 Dec 2015 14:26:04 -0800 (PST) From: David Rientjes Subject: Re: [PATCH v2] memory-hotplug: add automatic onlining policy for the newly added memory In-Reply-To: <20151222135520.1bcb2d18382f1e414864992c@linux-foundation.org> Message-ID: References: <1450801950-7744-1-git-send-email-vkuznets@redhat.com> <20151222135520.1bcb2d18382f1e414864992c@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Vitaly Kuznetsov , 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 , Naoya Horiguchi , Xishi Qiu , Mel Gorman , "K. Y. Srinivasan" , Igor Mammedov , Kay Sievers , Konrad Rzeszutek Wilk , Boris Ostrovsky On Tue, 22 Dec 2015, Andrew Morton wrote: > 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. > But isn't the premise of the changelog that this is currently being handled by the distribution? Perhaps I don't understand why this patch can't end up just introducing a sysfs tunable that is always present and can be set by initscripts of that distribution. I'd also suggest that hotplug_autoonline be renamed to auto_online_block. -- 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