[Xen-devel] [PATCH] xen: blkif.h: document linux xen-block multi-page ring implementation

[Bob Liu <bob.liu@xxxxxxxxxx>]

After commit 1b1586eeeb8c ("xenbus_client: Extend interface to
support multi-page ring"), Linux xenbus driver can support multi-page ring.

Based on this interface, we got some impressive improvements by using multi-page
ring in xen-block driver. If using 64 pages as the ring, the IOPS increased
about 15 times for the throughput testing.

The Linux implementation reuses two 'DEPRECATED' nodes('max-ring-pages' and
'num-ring-pages), so that nothing would be broken.
Also removed the power of 2 limit and updated the default/max value accordingly.

Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
---
 xen/include/public/io/blkif.h |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h
index 6baf7fb..0e34ae6 100644
--- a/xen/include/public/io/blkif.h
+++ b/xen/include/public/io/blkif.h
@@ -189,11 +189,11 @@
  *
  * max-ring-pages
  *      Values:         <uint32_t>
- *      Default Value:  1
- *      Notes:          DEPRECATED, 2, 3
+ *      Default Value:  32
+ *      Notes:          2, 3
  *
  *      The maximum supported size of the request ring buffer in units of
- *      machine pages.  The value must be a power of 2.
+ *      machine pages.
  *
  *------------------------- Backend Device Properties -------------------------
  *
@@ -302,11 +302,11 @@
  * num-ring-pages
  *      Values:         <uint32_t>
  *      Default Value:  1
- *      Maximum Value:  MAX(max-ring-pages,(0x1 << max-ring-page-order))
- *      Notes:          DEPRECATED, 2, 3
+ *      Maximum Value:  max-ring-pages
+ *      Notes:          2, 3
  *
  *      The size of the frontend allocated request ring buffer in units of
- *      machine pages.  The value must be a power of 2.
+ *      machine pages.
  *
  * feature-persistent
  *      Values:         0/1 (boolean)
-- 
1.7.10.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel