Re: [Xen-devel] [PATCH 0/2] xen/blkback: Aggressively shrink page pools if a memory pressure is detected

["Durrant, Paul" <pdurrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of
> SeongJae Park
> Sent: 04 December 2019 11:34
> To: konrad.wilk@xxxxxxxxxx; roger.pau@xxxxxxxxxx; axboe@xxxxxxxxx
> Cc: sj38.park@xxxxxxxxx; xen-devel@xxxxxxxxxxxxxxxxxxxx; linux-
> block@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Park, Seongjae
> <sjpark@xxxxxxxxxx>
> Subject: [Xen-devel] [PATCH 0/2] xen/blkback: Aggressively shrink page
> pools if a memory pressure is detected
> 
> Each `blkif` has a free pages pool for the grant mapping.  The size of
> the pool starts from zero and be increased on demand while processing
> the I/O requests.  If current I/O requests handling is finished or 100
> milliseconds has passed since last I/O requests handling, it checks and
> shrinks the pool to not exceed the size limit, `max_buffer_pages`.
> 
> Therefore, `blkfront` running guests can cause a memory pressure in the
> `blkback` running guest by attaching arbitrarily large number of block
> devices and inducing I/O.

OOI... How do guests unilaterally cause the attachment of arbitrary numbers of 
PV devices?

  Paul

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