From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-x242.google.com (mail-oi0-x242.google.com [IPv6:2607:f8b0:4003:c06::242]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 7CF1221A07A92 for ; Tue, 11 Sep 2018 09:50:59 -0700 (PDT) Received: by mail-oi0-x242.google.com with SMTP id l82-v6so48483843oih.11 for ; Tue, 11 Sep 2018 09:50:59 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20180910234341.4068.26882.stgit@localhost.localdomain> References: <20180910232615.4068.29155.stgit@localhost.localdomain> <20180910234341.4068.26882.stgit@localhost.localdomain> From: Dan Williams Date: Tue, 11 Sep 2018 09:50:57 -0700 Message-ID: Subject: Re: [PATCH 1/4] mm: Provide kernel parameter to allow disabling page init poisoning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Alexander Duyck Cc: pavel.tatashin@microsoft.com, Michal Hocko , linux-nvdimm , Dave Hansen , Linux Kernel Mailing List , Linux MM , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Andrew Morton , Ingo Molnar , "Kirill A. Shutemov" List-ID: On Mon, Sep 10, 2018 at 4:43 PM, Alexander Duyck wrote: > From: Alexander Duyck > > On systems with a large amount of memory it can take a significant amount > of time to initialize all of the page structs with the PAGE_POISON_PATTERN > value. I have seen it take over 2 minutes to initialize a system with > over 12GB of RAM. > > In order to work around the issue I had to disable CONFIG_DEBUG_VM and then > the boot time returned to something much more reasonable as the > arch_add_memory call completed in milliseconds versus seconds. However in > doing that I had to disable all of the other VM debugging on the system. > > In order to work around a kernel that might have CONFIG_DEBUG_VM enabled on > a system that has a large amount of memory I have added a new kernel > parameter named "page_init_poison" that can be set to "off" in order to > disable it. In anticipation of potentially more DEBUG_VM options wanting runtime control I'd propose creating a new "vm_debug=" option for this modeled after "slub_debug=" along with a CONFIG_DEBUG_VM_ON to turn on all options. That way there is more differentiation for debug cases like this that have significant performance impact when enabled. CONFIG_DEBUG_VM leaves optional debug capabilities disabled by default unless CONFIG_DEBUG_VM_ON is also set. _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm