Messages in this thread |  | | Subject | Re: [PATCH v3 1/3] xen-blkback: add a parameter for disabling of persistent grants | From | Jürgen Groß <> | Date | Tue, 22 Sep 2020 16:25:57 +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. But, there is no option to disable it. For > the reason, this commit adds a module parameter for disabling of the > feature. > > [1] https://wiki.xen.org/wiki/Xen_4.3_Block_Protocol_Scalability > > Signed-off-by: Anthony Liguori <aliguori@amazon.com> > Signed-off-by: SeongJae Park <sjpark@amazon.de> > --- > .../ABI/testing/sysfs-driver-xen-blkback | 9 ++++++++ > drivers/block/xen-blkback/xenbus.c | 22 ++++++++++++++----- > 2 files changed, 25 insertions(+), 6 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback > index ecb7942ff146..ac2947b98950 100644 > --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback > +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback > @@ -35,3 +35,12 @@ Description: > controls the duration in milliseconds that blkback will not > cache any page not backed by a grant mapping. > The default is 10ms. > + > +What: /sys/module/xen_blkback/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 backends. > + The default is Y (enable). > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c > index b9aa5d1ac10b..f4c8827fa0ad 100644 > --- a/drivers/block/xen-blkback/xenbus.c > +++ b/drivers/block/xen-blkback/xenbus.c > @@ -474,6 +474,12 @@ static void xen_vbd_free(struct xen_vbd *vbd) > vbd->bdev = NULL; > } > > +/* 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"); > + > static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, > unsigned major, unsigned minor, int readonly, > int cdrom) > @@ -519,6 +525,8 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, > if (q && blk_queue_secure_erase(q)) > vbd->discard_secure = true; > > + vbd->feature_gnt_persistent = feature_persistent ? 1 : 0;
Just assign the value instead of using the ternary operator?
With that changed you can add my
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen
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