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Re: [Xen-devel] [PATCH v3 0/1] xen/blkback: Squeeze page pools if a memory pressure

On 09.12.19 09:58, SeongJae Park wrote:
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 a large number of block devices and
inducing I/O.

I'm having problems to understand how a guest can attach a large number
of block devices without those having been configured by the host admin

If those devices have been configured, dom0 should be ready for that
number of devices, e.g. by having enough spare memory area for ballooned

So either I'm missing something here or your reasoning for the need of
the patch is wrong.


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