kernel_optimize_test/Documentation/ABI/testing/sysfs-driver-xen-blkback
Juergen Gross 973e5405f2 xen/blkback: don't keep persistent grants too long
Persistent grants are allocated until a threshold per ring is being
reached. Those grants won't be freed until the ring is being destroyed
meaning there will be resources kept busy which might no longer be
used.

Instead of freeing only persistent grants until the threshold is
reached add a timestamp and remove all persistent grants not having
been in use for a minute.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2018-08-27 12:12:03 -04:00

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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.