From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: Dave Hansen <dave.hansen@intel.com>,
linux-mm@kvack.org, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org
Cc: pavel.tatashin@microsoft.com, mhocko@suse.com,
dave.jiang@intel.com, jglisse@redhat.com,
rppt@linux.vnet.ibm.com, dan.j.williams@intel.com,
logang@deltatee.com, mingo@kernel.org,
kirill.shutemov@linux.intel.com
Subject: Re: [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling page init poisoning
Date: Tue, 25 Sep 2018 15:27:59 -0700 [thread overview]
Message-ID: <61358149-b233-6194-adcf-2c16b9112fd7@linux.intel.com> (raw)
In-Reply-To: <75dde720-c997-51a4-d2e2-8b08eb201550@intel.com>
On 9/25/2018 3:14 PM, Dave Hansen wrote:
> On 09/25/2018 01:38 PM, Alexander Duyck wrote:
>> On 9/25/2018 1:26 PM, Dave Hansen wrote:
>>> On 09/25/2018 01:20 PM, Alexander Duyck wrote:
>>>> + vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
>>>> + May slow down system boot speed, especially when
>>>> + enabled on systems with a large amount of memory.
>>>> + All options are enabled by default, and this
>>>> + interface is meant to allow for selectively
>>>> + enabling or disabling specific virtual memory
>>>> + debugging features.
>>>> +
>>>> + Available options are:
>>>> + P Enable page structure init time poisoning
>>>> + - Disable all of the above options
>>>
>>> Can we have vm_debug=off for turning things off, please? That seems to
>>> be pretty standard.
>>
>> No. The simple reason for that is that you had requested this work like
>> the slub_debug. If we are going to do that then each individual letter
>> represents a feature. That is why the "-" represents off. We cannot have
>> letters represent flags, and letters put together into words. For
>> example slub_debug=OFF would turn on sanity checks and turn off
>> debugging for caches that would have causes higher minimum slab orders.
>
> We don't have to have the same letters mean the same things for both
> options. We also can live without 'o' and 'f' being valid. We can
> *also* just say "don't do 'off'" if you want to enable things.
I'm not saying we do either. I would prefer it if we stuck to similar
behavior though. If we are going to do a slub_debug style parameter then
we should stick with similar behavior where "-" is used to indicate all
features off.
> I'd much rather have vm_debug=off do the right thing than have
> per-feature enable/disable. I know I'll *never* remember vm_debug=- and
> doing it this way will subject me to innumerable trips to Documentation/
> during my few remaining years.
>
> Surely you can make vm_debug=off happen. :)
I could, but then it is going to confuse people even more. I really feel
that if we want to do a slub_debug style interface we should use the
same switch for turning off all the features that they do for slub_debug.
>>> we need to document the defaults. I think the default is "all
>>> debug options are enabled", but it would be nice to document that.
>>
>> In the description I call out "All options are enabled by default, and this interface is meant to allow for selectively enabling or disabling".
>
> I found "all options are enabled by default" really confusing. Maybe:
>
> "Control debug features which become available when CONFIG_DEBUG_VM=y.
> When this option is not specified, all debug features are enabled. Use
> this option enable a specific subset."
>
> Then, let's actually say what the options do, and what their impact is:
>
> P Enable 'struct page' poisoning at initialization.
> (Slows down boot time).
>
From my perspective I just don't see how this changes much since it
conveys the same message I had conveyed in my description. Since it
looks like Andrew applied the patch feel free to submit your suggestion
here as a follow-up patch and I would be willing to review/ack it.
next prev parent reply other threads:[~2018-09-25 22:28 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-25 20:18 [PATCH v5 0/4] Address issues slowing persistent memory initialization Alexander Duyck
2018-09-25 20:19 ` [PATCH v5 1/4] mm: Remove now defunct NO_BOOTMEM from depends list for deferred init Alexander Duyck
2018-09-25 21:05 ` Mike Rapoport
2018-09-25 20:20 ` [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling page init poisoning Alexander Duyck
2018-09-25 20:26 ` Dave Hansen
2018-09-25 20:38 ` Alexander Duyck
2018-09-25 22:14 ` Dave Hansen
2018-09-25 22:27 ` Alexander Duyck [this message]
2018-09-26 7:38 ` Michal Hocko
2018-09-26 15:24 ` Alexander Duyck
2018-09-26 15:39 ` Michal Hocko
2018-09-26 15:41 ` Dave Hansen
2018-09-26 16:18 ` Alexander Duyck
2018-09-26 15:36 ` Dave Hansen
2018-09-26 22:36 ` Andrew Morton
2018-09-25 20:20 ` [PATCH v5 3/4] mm: Create non-atomic version of SetPageReserved for init use Alexander Duyck
2018-09-25 20:21 ` [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap Alexander Duyck
2018-09-26 7:55 ` Michal Hocko
2018-09-26 18:25 ` Alexander Duyck
2018-09-26 18:52 ` Dan Williams
2018-09-27 11:20 ` Michal Hocko
2018-09-27 11:09 ` Michal Hocko
2018-09-27 12:25 ` Oscar Salvador
2018-09-27 13:13 ` Michal Hocko
2018-09-27 14:50 ` Oscar Salvador
2018-09-27 15:41 ` David Hildenbrand
2018-09-28 8:12 ` Oscar Salvador
2018-09-28 8:44 ` Oscar Salvador
2018-09-28 15:50 ` Dan Williams
2018-09-27 12:32 ` Oscar Salvador
2018-10-08 21:01 ` Dan Williams
2018-10-08 21:38 ` Alexander Duyck
2018-10-08 22:00 ` Dan Williams
2018-10-08 22:07 ` Alexander Duyck
2018-10-08 22:36 ` Alexander Duyck
2018-10-08 22:59 ` Dan Williams
2018-10-08 23:34 ` [mm PATCH] memremap: Fix reference count for pgmap in devm_memremap_pages Alexander Duyck
2018-10-09 0:20 ` Dan Williams
2018-10-09 17:00 ` [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap Yi Zhang
2018-10-09 18:04 ` Dan Williams
2018-10-09 20:26 ` Alexander Duyck
2018-10-09 21:19 ` Dan Williams
2018-10-10 12:52 ` Yi Zhang
2018-10-10 15:27 ` Alexander Duyck
2018-10-11 8:17 ` Yi Zhang
2018-10-10 9:58 ` Michal Hocko
2018-10-10 16:39 ` Alexander Duyck
2018-10-10 17:24 ` Michal Hocko
2018-10-10 17:39 ` Alexander Duyck
2018-10-10 17:53 ` Michal Hocko
2018-10-10 18:13 ` Alexander Duyck
2018-10-10 18:52 ` Michal Hocko
2018-10-11 8:55 ` Michal Hocko
2018-10-11 17:38 ` Alexander Duyck
2018-10-11 18:22 ` Dan Williams
2018-10-17 7:52 ` Michal Hocko
2018-10-17 15:02 ` Alexander Duyck
2018-10-29 14:12 ` Michal Hocko
2018-10-29 15:59 ` Alexander Duyck
2018-10-29 16:35 ` Michal Hocko
2018-10-29 17:01 ` Alexander Duyck
2018-10-29 17:24 ` Michal Hocko
2018-10-29 17:34 ` Dan Williams
2018-10-29 17:45 ` Michal Hocko
2018-10-29 17:42 ` Alexander Duyck
2018-10-29 18:18 ` Michal Hocko
2018-10-29 19:59 ` Alexander Duyck
2018-10-30 6:29 ` Michal Hocko
2018-10-30 6:55 ` Dan Williams
2018-10-30 8:17 ` Michal Hocko
2018-10-30 15:57 ` Dan Williams
2018-10-30 8:05 ` Oscar Salvador
2018-10-29 15:49 ` Dan Williams
2018-10-29 15:56 ` Michal Hocko
2018-10-10 18:18 ` Dan Williams
2018-10-11 8:39 ` Yi Zhang
2018-10-11 15:38 ` Alexander Duyck
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