linux-kernel - Re: [PATCH v3 0/5] xen/blk: persistent grant rework

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Date:   Fri, 24 Aug 2018 15:52:23 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Roger Pau Monné <roger.pau@...rix.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-block@...r.kernel.org, konrad.wilk@...cle.com,
        axboe@...nel.dk, boris.ostrovsky@...cle.com
Subject: Re: [PATCH v3 0/5] xen/blk: persistent grant rework

On 17/08/18 17:59, Roger Pau Monné wrote:
> On Mon, Aug 13, 2018 at 04:01:09PM +0200, Juergen Gross wrote:
>> Persistent grants are used in the Xen's blkfront/blkback drivers to
>> avoid mapping/unmapping of I/O buffers in the backend for each I/O.
>>
>> While this speeds up processing quite a bit there are problems related
>> to persistent grants in some configurations: domains with multiple
>> block devices making use of persistent grants might suffer from a lack
>> of grants if each of the block devices experienced a high I/O load at
>> some time. This is due to the number of persistent grants per device
>> only to be limited by a rather high maximum value, but never being
>> released even in case of longer times without any I/O.
>>
>> This series modifies xen-blkback to unmap any domU page mapped via a
>> persistent grant after a timeout (default: 60 seconds). The timeout
>> is set to its default value again when a persistent grant has been
>> used for an I/O.
>>
>> xen-blkfront is modified to scan every 10 seconds for persistent grants
>> not in use by blkback any more and to remove such grants.
>>
>> The last 3 patches are small cleanups of blkfront and blkback drivers.
>>
>> V3:
>> - patch 1: make timeout parameter static
> 
> Konrad if you are OK with this series, could you please send a pull
> request to Jens?

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Juergen