Re: [BK PATCH 1/2] Remove NGROUPS hardlimit (resend w/o qsort)

[Andrew Morton]

Tim Hockin wrote:
> 
> > 10,000 bits isn't much.  Maybe:
> 
> That's 10000 USED bits.  Remember groups are non-contiguously allocated.  If
> a task is a member of just groups 32767 and 65535, you'll get one bit per
> page used, and when they call getgroups() you need to pull it apart and
> return an array of gid_t.
> 

Well that's what I was asking.

What is the maximum group ID?  0xffffffff?

In that case a radix tree _might_ suit.  All you need to put in the
node is a (void *)1 or (void *)0.  But it won't be very space-efficient
for really sparse groups.