Re: [Xen-devel] [PATCH] mm/page_alloc: always scrub pages given to the allocator

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 01.10.18 at 16:28, <sergey.dyasli@xxxxxxxxxx> wrote:
> On Mon, 2018-10-01 at 14:54 +0100, George Dunlap wrote:
>> Right, the whole point of idle loop scrubbing is that you *don't*
>> syncronously wait for *all* the memory to finish scrubbing before you
>> can use part of it.  So why is this an issue for you guys -- what
>> concrete problem did it cause, that the full amount of memory took 40s
>> to finish scrubbing rather than only 8s?
> 
> There is no issue at the moment. Using idle loop to scrub all the memory
> is just not viable: it doesn't scale. How long does it currently take
> to bootscrub a multi-Tb system? If it takes a few minutes then I fear
> that it might take an hour to idle-scrub it.

But that's fine, at least in theory, as long as no scrubbing will be
skipped when it was actually needed. The system will be slightly
more busy until done with the scrubbing, but that's exactly the
expected price to pay for the cut down on boot time.

Jan



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