Question about ION carveout heap support partial cache flush

On Mon, Aug 27, 2012 at 4:56 PM, zhangfei gao [off-list ref] wrote:

Any suggestion of flushing cache according to cache line, instead of PAGE_SIZE.
In order to get specific area, we use addr from user directly, which
may not be the PAGE start.

We have some usage case to flush cache according to cache line.
CPU - cache - ddr - gpu
1. For correctness, driver only flush used size, if align to PAGE_SIZE,
other area may be flushed by mistake.
2. for efficiency, cache line align will be perfered.

I think that maybe flushing PAGE_SIZE is acceptable. ION/PMEM is always designed
for large memory sharing. Maybe you can monitor the partial flushing
user case, I doubt
they're always flushing several pages, not several cachelines.