Messages in this thread | | | Subject | Re: [PATCH v3 2/3] xen-blkfront: add a parameter for disabling of persistent grants | From | Jürgen Groß <> | Date | Tue, 22 Sep 2020 16:27:03 +0200 |
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On 22.09.20 16:15, SeongJae Park wrote: > From: SeongJae Park <sjpark@amazon.de> > > Persistent grants feature provides high scalability. On some small > systems, however, it could incur data copy overheads[1] and thus it is > required to be disabled. It can be disabled from blkback side using a > module parameter, 'feature_persistent'. But, it is impossible from > blkfront side. For the reason, this commit adds a blkfront module > parameter for disabling of the feature. > > [1] https://wiki.xen.org/wiki/Xen_4.3_Block_Protocol_Scalability > > Signed-off-by: SeongJae Park <sjpark@amazon.de> > --- > .../ABI/testing/sysfs-driver-xen-blkfront | 9 +++++++++ > drivers/block/xen-blkfront.c | 20 ++++++++++++++----- > 2 files changed, 24 insertions(+), 5 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkfront b/Documentation/ABI/testing/sysfs-driver-xen-blkfront > index c0a6cb7eb314..9c31334cb2e6 100644 > --- a/Documentation/ABI/testing/sysfs-driver-xen-blkfront > +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkfront > @@ -8,3 +8,12 @@ Description: > is 32 - higher value means more potential throughput but more > memory usage. The backend picks the minimum of the frontend > and its default backend value. > + > +What: /sys/module/xen_blkfront/parameters/feature_persistent > +Date: September 2020 > +KernelVersion: 5.10 > +Contact: SeongJae Park <sjpark@amazon.de> > +Description: > + Whether to enable the persistent grants feature or not. Note > + that this option only takes effect on newly created frontends. > + The default is Y (enable). > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > index 91de2e0755ae..b2d3b1262404 100644 > --- a/drivers/block/xen-blkfront.c > +++ b/drivers/block/xen-blkfront.c > @@ -1866,8 +1866,8 @@ static int talk_to_blkback(struct xenbus_device *dev, > message = "writing protocol"; > goto abort_transaction; > } > - err = xenbus_printf(xbt, dev->nodename, > - "feature-persistent", "%u", 1); > + err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", > + info->feature_persistent); > if (err) > dev_warn(&dev->dev, > "writing persistent grants feature to xenbus"); > @@ -1941,6 +1941,13 @@ static int negotiate_mq(struct blkfront_info *info) > } > return 0; > } > + > +/* Enable the persistent grants feature. */ > +static bool feature_persistent = true; > +module_param(feature_persistent, bool, 0644); > +MODULE_PARM_DESC(feature_persistent, > + "Enables the persistent grants feature"); > + > /** > * Entry point to this code when a new device is created. Allocate the basic > * structures and the ring buffer for communication with the backend, and > @@ -2007,6 +2014,8 @@ static int blkfront_probe(struct xenbus_device *dev, > info->vdevice = vdevice; > info->connected = BLKIF_STATE_DISCONNECTED; > > + info->feature_persistent = feature_persistent ? 1 : 0;
Just use the value.
With that changed:
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen
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