Re: [patch] aio: remove aio-max-nr and instead use the memlock rlimit to limit the number of pages pinned for the aio completion ring

[Avi Kivity <avi@redhat.com>]

Jeff Moyer wrote:
> Hi,
>
> Believe it or not, I get numerous questions from customers about the
> suggested tuning value of aio-max-nr.  aio-max-nr limits the total
> number of io events that can be reserved, system wide, for aio
> completions.  Each time io_setup is called, a ring buffer is allocated
> that can hold nr_events I/O completions.  That ring buffer is then
> mapped into the process' address space, and the pages are pinned in
> memory.  So, the reason for this upper limit (I believe) is to keep a
> malicious user from pinning all of kernel memory.  Now, this sounds like
> a much better job for the memlock rlimit to me, hence the following
> patch.
>   

Is it not possible to get rid of the pinning entirely?  Pinning 
interferes with page migration which is important for NUMA, among other 
issues.

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