Following a proposal by Ivan, defer cache index initialization inside cache-membuffer to the first write access. That allows for multi-GB caches to be created virtually instantly (assuming the OS reserves memory sufficiently quickly).
Following a proposal by Ivan, defer cache index initialization
inside cache-membuffer to the first write access. That allows
for multi-GB caches to be created virtually instantly (assuming
the OS reserves memory sufficiently quickly).

* subversion/libsvn_subr/cache-membuffer.c
  (GROUP_INIT_GRANULARITY): new constant
  (svn_membuffer_t): add group_initialized bit vector
  (is_group_initialized): new utility to check for a groups' init. status
  (initialize_group): new function to initialize a group
  (find_entry): auto-initialize groups upon access
  (svn_cache__membuffer_cache_create): only initialize the group 
   init. status instead of the actual directory

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1104236 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion