Change in mmap driver performance from 2..6.38 to 2.6.39

I have a device drier that uses a mmap'd section of memory to expose dma buffers to user space. (https://github.com/balister/linux-omap-philip/blob/e100-2.6.38/drivers/misc/usrp_e.c).

I have it running on the 2.6.38 and 2.6.39 kernel, but it looks like read performance is much slower in the .39 version than the .28 version.

Does anyone know what changed between these two kernel versions and how it might fix it?

Thanks,

Philip

Maybe try git bisect it to some commit? You can use quilt to keep applying the temporary patches needed in between test builds for your driver.. Or maybe git allows that somehow too.

Tony