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authorRoger Pau Monne <roger.pau@citrix.com>2013-04-17 20:18:57 +0200
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-04-18 09:29:23 -0400
commit3f3aad5e6686ed49242bbf86de378b39f119ec9d (patch)
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parentc6cc142dac52e62e1e8a2aff5de1300202b96c66 (diff)
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xen-blkback: implement LRU mechanism for persistent grants
This mechanism allows blkback to change the number of grants persistently mapped at run time. The algorithm uses a simple LRU mechanism that removes (if needed) the persistent grants that have not been used since the last LRU run, or if all grants have been used it removes the first grants in the list (that are not in use). The algorithm allows the user to change the maximum number of persistent grants, by changing max_persistent_grants in sysfs. Since we are storing the persistent grants used inside the request struct (to be able to mark them as "unused" when unmapping), we no longer need the bitmap (unmap_seg). Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: xen-devel@lists.xen.org Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/stable/sysfs-bus-xen-backend10
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/ABI/stable/sysfs-bus-xen-backend b/Documentation/ABI/stable/sysfs-bus-xen-backend
index e04afe0cca99..947db11350bc 100644
--- a/Documentation/ABI/stable/sysfs-bus-xen-backend
+++ b/Documentation/ABI/stable/sysfs-bus-xen-backend
@@ -81,3 +81,13 @@ 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: 3.10
+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.