| Message ID | 20200922141549.26154-2-sjpark@amazon.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen-blk(back|front): Let users disable persistent grants | expand |
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
On Tue, 22 Sep 2020 16:25:57 +0200 "Jürgen Groß" <jgross@suse.com> wrote: > 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? I will do so in the next version. > > With that changed you can add my > > Reviewed-by: Juergen Gross <jgross@suse.com> Thank you for your kind, quick, and detailed review! Thanks, SeongJae Park
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; + pr_debug("Successful creation of handle=%04x (dom=%u)\n", handle, blkif->domid); return 0; @@ -906,7 +914,8 @@ 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", + be->blkif->vbd.feature_gnt_persistent); if (err) { xenbus_dev_fatal(dev, err, "writing %s/feature-persistent", dev->nodename); @@ -1067,7 +1076,6 @@ static int connect_ring(struct backend_info *be) { struct xenbus_device *dev = be->dev; struct xen_blkif *blkif = be->blkif; - unsigned int pers_grants; char protocol[64] = ""; int err, i; char *xspath; @@ -1093,9 +1101,11 @@ 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); - blkif->vbd.feature_gnt_persistent = pers_grants; + if (blkif->vbd.feature_gnt_persistent) + blkif->vbd.feature_gnt_persistent = + xenbus_read_unsigned(dev->otherend, + "feature-persistent", 0); + blkif->vbd.overflow_max_grants = 0; /* @@ -1118,7 +1128,7 @@ static int connect_ring(struct backend_info *be) pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename, blkif->nr_rings, blkif->blk_protocol, protocol, - pers_grants ? "persistent grants" : ""); + blkif->vbd.feature_gnt_persistent ? "persistent grants" : ""); ring_page_order = xenbus_read_unsigned(dev->otherend, "ring-page-order", 0);