From: Alexander Duyck <alexander.duyck@gmail.com>
To: mhocko@kernel.org
Cc: pavel.tatashin@microsoft.com, linux-nvdimm@lists.01.org,
Dave Hansen <dave.hansen@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
jglisse@redhat.com,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 1/4] mm: Provide kernel parameter to allow disabling page init poisoning
Date: Wed, 12 Sep 2018 07:49:06 -0700 [thread overview]
Message-ID: <CAKgT0UdvhV7U5Zniq=KskXz2QsRP8C7ctr5=ZtJwYAVpBT-RHw@mail.gmail.com> (raw)
In-Reply-To: <20180912141053.GL10951@dhcp22.suse.cz>
On Wed, Sep 12, 2018 at 7:10 AM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Mon 10-09-18 16:43:41, Alexander Duyck wrote:
> > From: Alexander Duyck <alexander.h.duyck@intel.com>
> >
> > 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.
>
> I am still not convinced that this all is worth the additional code. It
> is much better than a new config option for sure. If we really want this
> though then I suggest that the parameter handler should note the
> disabled state (when CONFIG_DEBUG_VM is on) to the kernel log. I would
> also make it explicit who might want to do that in the parameter
> description.
Anything specific in terms of the kernel log message we are looking
for? I'll probably just go with "Page struct poisoning disabled by
kernel command line option 'page_init_poison'" or something along
those lines.
> > + page_init_poison= [KNL] Boot-time parameter changing the
> > + state of poisoning of page structures during early
> > + boot. Used to verify page metadata is not accessed
> > + prior to initialization. Available with
> > + CONFIG_DEBUG_VM=y.
> > + off: turn off poisoning
> > + on: turn on poisoning (default)
> > +
>
> what about the following wording or something along those lines
>
> Boot-time parameter to control struct page poisoning which is a
> debugging feature to catch unitialized struct page access. This option
> is available only for CONFIG_DEBUG_VM=y and it affects boot time
> (especially on large systems). If there are no poisoning bugs reported
> on the particular system and workload it should be safe to disable it to
> speed up the boot time.
That works for me. I will update it for the next release.
Thanks.
- Alex
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next prev parent reply other threads:[~2018-09-12 14:49 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-10 23:43 [PATCH 0/4] Address issues slowing persistent memory initialization Alexander Duyck
2018-09-10 23:43 ` [PATCH 1/4] mm: Provide kernel parameter to allow disabling page init poisoning Alexander Duyck
2018-09-11 0:35 ` Alexander Duyck
2018-09-11 16:50 ` Dan Williams
2018-09-11 20:01 ` Alexander Duyck
2018-09-11 20:24 ` Dan Williams
2018-09-12 13:24 ` Pasha Tatashin
2018-09-12 14:10 ` Michal Hocko
2018-09-12 14:49 ` Alexander Duyck [this message]
2018-09-12 15:23 ` Dave Hansen
2018-09-12 16:36 ` Alexander Duyck
2018-09-12 16:43 ` Dave Hansen
2018-09-10 23:43 ` [PATCH 2/4] mm: Create non-atomic version of SetPageReserved for init use Alexander Duyck
2018-09-12 13:28 ` Pasha Tatashin
2018-09-10 23:43 ` [PATCH 3/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap Alexander Duyck
2018-09-11 7:49 ` kbuild test robot
2018-09-11 7:54 ` kbuild test robot
2018-09-11 22:35 ` Dan Williams
2018-09-12 0:51 ` Alexander Duyck
2018-09-12 0:59 ` Dan Williams
2018-09-12 13:59 ` Pasha Tatashin
2018-09-12 15:48 ` Alexander Duyck
2018-09-12 15:54 ` Pasha Tatashin
2018-09-12 16:44 ` Alexander Duyck
2018-09-12 16:50 ` Dan Williams
2018-09-12 17:46 ` Pasha Tatashin
2018-09-12 19:11 ` Dan Williams
2018-09-10 23:44 ` [PATCH 4/4] nvdimm: Trigger the device probe on a cpu local to the device Alexander Duyck
2018-09-11 0:37 ` Alexander Duyck
2018-09-12 5:48 ` Dan Williams
2018-09-12 13:44 ` Pasha Tatashin
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