.../ABI/testing/sysfs-driver-xen-blkback | 8 ++++++++ drivers/block/xen-blkback/xenbus.c | 17 ++++++++++++++--- 2 files changed, 22 insertions(+), 3 deletions(-)
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;
+module_param_named(feature_persistent, feature_persistent, int, 0644);
+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);
if (err) {
xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
dev->nodename);
@@ -1093,8 +1100,12 @@ static int connect_ring(struct backend_info *be)
xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
return -ENOSYS;
}
- pers_grants = xenbus_read_unsigned(dev->otherend, "feature-persistent",
- 0);
+ if (feature_persistent)
+ pers_grants = xenbus_read_unsigned(dev->otherend,
+ "feature-persistent", 0);
+ else
+ pers_grants = 0;
+
blkif->vbd.feature_gnt_persistent = pers_grants;
blkif->vbd.overflow_max_grants = 0;
--
2.17.1
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
On Tue, 22 Sep 2020 09:18:05 +0200 "Jürgen Groß" <jgross@suse.com> wrote: > 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. Oops, I will. > > > +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. Indeed. I will fix these as you recommended in the next spin. Thanks, SeongJae Park
On Tue, Sep 22, 2020 at 09:01:25AM +0200, 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.
Would it be better suited to have it per guest?
>
> [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;
> +module_param_named(feature_persistent, feature_persistent, int, 0644);
> +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);
> if (err) {
> xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
> dev->nodename);
> @@ -1093,8 +1100,12 @@ static int connect_ring(struct backend_info *be)
> xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
> return -ENOSYS;
> }
> - pers_grants = xenbus_read_unsigned(dev->otherend, "feature-persistent",
> - 0);
> + if (feature_persistent)
> + pers_grants = xenbus_read_unsigned(dev->otherend,
> + "feature-persistent", 0);
> + else
> + pers_grants = 0;
> +
> blkif->vbd.feature_gnt_persistent = pers_grants;
> blkif->vbd.overflow_max_grants = 0;
>
> --
> 2.17.1
>
On Wed, 23 Sep 2020 16:09:30 -0400 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote: > On Tue, Sep 22, 2020 at 09:01:25AM +0200, 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. > > Would it be better suited to have it per guest? The latest version of this patchset[1] supports blkfront side disablement. Could that partially solves your concern? [1] https://lore.kernel.org/xen-devel/20200923061841.20531-1-sjpark@amazon.com/ Thanks, SeongJae Park
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