Re: [PATCH] uio: add UIO_MEM_CUSTOM support

From: Xiubo Li
Date: Wed Feb 15 2017 - 20:34:58 EST



diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index fba021f..6ca0ae0 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -708,6 +708,8 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
case UIO_MEM_LOGICAL:
case UIO_MEM_VIRTUAL:
return uio_mmap_logical(vma);
+ case UIO_MEM_CUSTOM:
+ return 0;
How does this help?
For example, the TCMU will use the map area as ISCSI commands & data ring
buffer(uio0 --> map0). Currently the TCMU will using the fixed small size map
area as the ring buffer, but this will be the bottleneck for high iops.

Without knowing how large it is enough, so the new scheme will use the fixed
small ring buffer area(about 64M ~ 128M) + dynamically "growing" ring buffer
area(about 1.5G).

The fixed small area will be using vmalloc() when initializing, and dynamically
"growing" area will must use kmalloc() for some reasons.

...

Can you provide an update to the documentation in
Documentation/driver-api/uio-howto.rst to show how to use this?
Yes, I will update this.

Thanks.

BRs
Xiubo

thanks,

greg k-h