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+What: /sys/module/xen_blkback/parameters/max_buffer_pages
+Date: March 2013
+KernelVersion: 3.11
+Contact: Roger Pau Monné <roger.pau@citrix.com>
+Description:
+ Maximum number of free pages to keep in each block
+ backend buffer.
+
+What: /sys/module/xen_blkback/parameters/max_persistent_grants
+Date: March 2013
+KernelVersion: 3.11
+Contact: Roger Pau Monné <roger.pau@citrix.com>
+Description:
+ Maximum number of grants to map persistently in
+ blkback. If the frontend tries to use more than
+ max_persistent_grants, the LRU kicks in and starts
+ removing 5% of max_persistent_grants every 100ms.
+
+What: /sys/module/xen_blkback/parameters/persistent_grant_unused_seconds
+Date: August 2018
+KernelVersion: 4.19
+Contact: Roger Pau Monné <roger.pau@citrix.com>
+Description:
+ How long a persistent grant is allowed to remain
+ allocated without being in use. The time is in
+ seconds, 0 means indefinitely long.
+ The default is 60 seconds.
+
+What: /sys/module/xen_blkback/parameters/buffer_squeeze_duration_ms
+Date: December 2019
+KernelVersion: 5.6
+Contact: Maximilian Heyne <mheyne@amazon.de>
+Description:
+ When memory pressure is reported to blkback this option
+ 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: Maximilian Heyne <mheyne@amazon.de>
+Description:
+ Whether to enable the persistent grants feature or not. Note
+ that this option only takes effect on newly connected backends.
+ The default is Y (enable).