linux-kernel - Re: [Xen-devel] [PATCH v7 1/3] xenbus/backend: Add memory pressure handler callback

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Date:   Thu, 12 Dec 2019 10:46:00 +0100
From:   Roger Pau Monné <roger.pau@...rix.com>
To:     SeongJae Park <sj38.park@...il.com>
CC:     <jgross@...e.com>, <axboe@...nel.dk>, <konrad.wilk@...cle.com>,
        <linux-block@...r.kernel.org>, <sjpark@...zon.com>,
        <pdurrant@...zon.com>, SeongJae Park <sjpark@...zon.de>,
        <linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>
Subject: Re: [Xen-devel] [PATCH v7 1/3] xenbus/backend: Add memory pressure
 handler callback

On Wed, Dec 11, 2019 at 06:10:14PM +0000, SeongJae Park wrote:
> Granting pages consumes backend system memory.  In systems configured
> with insufficient spare memory for those pages, it can cause a memory
> pressure situation.  However, finding the optimal amount of the spare
> memory is challenging for large systems having dynamic resource
> utilization patterns.  Also, such a static configuration might lack
> flexibility.
> 
> To mitigate such problems, this commit adds a memory reclaim callback to
> 'xenbus_driver'.  If a memory pressure is detected, 'xenbus' requests
> every backend driver to volunarily release its memory.
> 
> Note that it would be able to improve the callback facility for more
> sophisticated handlings of general pressures.  For example, it would be
> possible to monitor the memory consumption of each device and issue the
> release requests to only devices which causing the pressure.  Also, the
> callback could be extended to handle not only memory, but general
> resources.  Nevertheless, this version of the implementation defers such
> sophisticated goals as a future work.
> 
> Reviewed-by: Juergen Gross <jgross@...e.com>
> Signed-off-by: SeongJae Park <sjpark@...zon.de>

Reviewed-by: Roger Pau Monné <roger.pau@...rix.com>

Thanks, Roger.