Messages in this thread | | | Subject | Re: [PATCH] xen-blkback: add a parameter for disabling of persistent grants | From | Jürgen Groß <> | Date | Tue, 22 Sep 2020 09:18:05 +0200 |
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On 22.09.20 09:01, 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 overhead[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 | 8 ++++++++ > drivers/block/xen-blkback/xenbus.c | 17 ++++++++++++++--- > 2 files changed, 22 insertions(+), 3 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback > index ecb7942ff146..0c42285c75ee 100644 > --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback > +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback > @@ -35,3 +35,11 @@ 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. > + The default is 1 (enable). > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c > index b9aa5d1ac10b..9c03d70469f4 100644 > --- a/drivers/block/xen-blkback/xenbus.c > +++ b/drivers/block/xen-blkback/xenbus.c > @@ -879,6 +879,12 @@ static void reclaim_memory(struct xenbus_device *dev) > > /* ** Connection ** */ > > +/* Enable the persistent grants feature. */ > +static unsigned int feature_persistent = 1;
Use bool, please.
> +module_param_named(feature_persistent, feature_persistent, int, 0644);
module_param()
> +MODULE_PARM_DESC(feature_persistent, > + "Enables the persistent grants feature"); > + > /* > * Write the physical details regarding the block device to the store, and > * switch to Connected state. > @@ -906,7 +912,8 @@ static void connect(struct backend_info *be) > > xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support); > > - err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1); > + err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", > + feature_persistent ? 1 : 0);
Using bool above should allow to just use the value of feature_persistent here.
Juergen
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