linux-kernel - Re: [PATCH v5 1/2] xenbus/backend: Add memory pressure handler callback

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Message-ID: <7260cdce-7488-5045-0572-021a0ef191ac@suse.com>
Date:   Tue, 10 Dec 2019 09:17:38 +0100
From:   Jürgen Groß <jgross@...e.com>
To:     SeongJae Park <sj38.park@...il.com>, sjpark@...zon.com
Cc:     axboe@...nel.dk, konrad.wilk@...cle.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        pdurrant@...zon.com, roger.pau@...rix.com,
        xen-devel@...ts.xenproject.org, SeongJae Park <sjpark@...zon.de>
Subject: Re: [PATCH v5 1/2] xenbus/backend: Add memory pressure handler
 callback

On 10.12.19 09:06, 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 a
> flexibility.
> 
> To mitigate such problems, this commit adds a memory reclaim callback to
> 'xenbus_driver'.  Using this facility, 'xenbus' would be able to monitor
> a memory pressure and request specific devices of specific backend
> drivers which causing the given pressure to voluntarily release its
> memory.
> 
> That said, this commit simply requests every callback registered driver
> to release its memory for every domain, rather than issueing the
> requests to the drivers and the domain in charge.  Such things will be
> done in a futur.  Also, this commit focuses on memory only.  However, it
> would be ablt to be extended for general resources.
> 
> Signed-off-by: SeongJae Park <sjpark@...zon.de>

Reviewed-by: Juergen Gross <jgross@...e.com>


Juergen