Re: [PATCH] xen-blkback: add a parameter for disabling of persistent grants

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 22.09.20 09:01, SeongJae Park wrote:
From: SeongJae Park <sjpark@xxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: SeongJae Park <sjpark@xxxxxxxxx>
---
  .../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@xxxxxxxxx>
+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



[Index of Archives]     [Linux RAID]     [Linux SCSI]     [Linux ATA RAID]     [IDE]     [Linux Wireless]     [Linux Kernel]     [ATH6KL]     [Linux Bluetooth]     [Linux Netdev]     [Kernel Newbies]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Device Mapper]

  Powered by Linux