On Tue, Jan 26, 2016 at 6:15 PM, Joonsoo Kim <iamjoonsoo.kim(a)lge.com> wrote:
On Tue, Jan 26, 2016 at 05:37:38PM -0800, Dan Williams wrote:
> On Tue, Jan 26, 2016 at 5:18 PM, Joonsoo Kim <iamjoonsoo.kim(a)lge.com> wrote:
> > Please refer my previous attempt to add a new zone,
> > https://lkml.org/lkml/2015/2/12/84
> > It salvages a bit from SECTION_WIDTH by increasing section size.
> > Similarly, I guess we can reduce NODE_WIDTH if needed although
> > it could cause to reduce maximum node size.
> Dave pointed out to me that LAST__PID_SHIFT might be a better
> candidate to reduce to 7 bits. That field is for storing pids which
> are already bigger than 8 bits. If it is relying on the fact that
> pids don't rollover very often then likely the impact of 7-bits
> instead of 8 will be minimal.
Hmm... I'm not sure it's possible or not, but, it looks not a general
solution. It will solve your problem because you are using 64 bit arch
but other 32 bit archs can't get the benefit.
This is where the ZONE_CMA and ZONE_DEVICE efforts diverge.
ZONE_DEVICE is meant to enable DMA access to hundreds of gigagbytes of
persistent memory. A 64-bit-only limitation for ZONE_DEVICE is