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From: Michal Hocko <mhocko@kernel.org>
To: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: pavel.tatashin@microsoft.com, linux-nvdimm@lists.01.org,
	dave.hansen@intel.com, linux-kernel@vger.kernel.org,
	mingo@kernel.org, linux-mm@kvack.org, jglisse@redhat.com,
	rppt@linux.vnet.ibm.com, akpm@linux-foundation.org,
	kirill.shutemov@linux.intel.com
Subject: Re: [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling page init poisoning
Date: Wed, 26 Sep 2018 17:39:21 +0200	[thread overview]
Message-ID: <20180926153921.GC6278@dhcp22.suse.cz> (raw)
In-Reply-To: <c57da51a-009a-9500-4dc5-1d9912e78abd@linux.intel.com>

On Wed 26-09-18 08:24:56, Alexander Duyck wrote:
> On 9/26/2018 12:38 AM, Michal Hocko wrote:
> > On Tue 25-09-18 13:20:12, 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
> > 
> > I agree with Dave that this is confusing as hell. So what does vm_debug
> > (without any options means). I assume it's NOP and all debugging is
> > enabled and that is the default. What if I want to disable _only_ the
> > page struct poisoning. The weird lookcing `-' will disable all other
> > options that we might gather in the future.
> 
> With no options it works just like slub_debug and enables all available
> options. So in our case it is a NOP since we wanted the debugging enabled by
> default.

But isn't slub_debug more about _adding_ debugging features? While you
want to effectively disbale some debugging features here? So if you want
to follow that pattern then it would be something like
vm_debug_disable=page_poisoning,$OTHER_FUTURE_DEBUG_OPTIONS

why would you want to enable something when CONFIG_DEBUG_VM=y just
enables everything?

> > Why cannot you simply go with [no]vm_page_poison[=on/off]?
> 
> That is what I had to begin with, but Dave Hansen and Dan Williams suggested
> that I go with a slub_debug style interface so we could extend it in the
> future.

Please let's not over-engineer this. If you really need an umbrella
parameter then make a list of things to disable.
-- 
Michal Hocko
SUSE Labs
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  reply	other threads:[~2018-09-26 15:39 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
2018-09-26  7:38   ` Michal Hocko
2018-09-26 15:24     ` Alexander Duyck
2018-09-26 15:39       ` Michal Hocko [this message]
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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