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xen-blkfront: Introduce a 'max' module parameter to alter the amount of indirect segments. 

The max module parameter (by default 32) is the maximum number of
segments that the frontend will negotiate with the backend for indirect
descriptors.  Higher value means more potential throughput but more
memory usage. The backend picks the minimum of the frontend and its
default backend value.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2013-05-15 10:39:34 -04:00
parent b7649158a0
commit 2d5dc3ba85
2 changed files with 12 additions and 0 deletions
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10
Documentation/ABI/testing/sysfs-driver-xen-blkfront Normal file
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@ -0,0 +1,10 @@
What: /sys/module/xen_blkfront/parameters/max
Date: June 2013
KernelVersion: 3.11
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
Maximum number of segments that the frontend will negotiate
with the backend for indirect descriptors. The default value
is 32 - higher value means more potential throughput but more
memory usage. The backend picks the minimum of the frontend
and its default backend value.

2
drivers/block/xen-blkfront.c
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@ -95,6 +95,8 @@ static const struct block_device_operations xlvbd_block_fops;
*/
static unsigned int xen_blkif_max_segments = 32;
module_param_named(max, xen_blkif_max_segments, int, S_IRUGO);
MODULE_PARM_DESC(max, "Maximum amount of segments in indirect requests (default is 32)");
#define BLK_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE)