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SubjectRe: [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling page init poisoning
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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.

Either I can do this as a single parameter that supports on/off
semantics, or I can support it as a slub_debug type parameter that does
flags based on the input options. I would rather not muddy things by
trying to do both.

> Also, 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".


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