On Mon, Sep 10, 2018 at 4:43 PM, Alexander Duyck <alexander.duyck@xxxxxxxxx> wrote: > From: Alexander Duyck <alexander.h.duyck@xxxxxxxxx> > > 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.
