[Bug nscd/1204] New: nscd cannot extend memory heap sizes

["nick at sqrt dot co dot uk" <sourceware-bugzilla at sources dot redhat dot com>]

The change in nscd to use mmap for memory allocation of caches presents a
problem in that once the cache is full, mempool_alloc cannot extend the size of
the cache because 'mremap' will always fail.

   4279: no more memory for database 'group'

$ nscd -g shows:
         216064  total data pool size
         214664  used data pool size
              7  memory allocations failed

The problem is that for a system with large group memberships (i.e. several
thousand users), which are held in LDAP databases, as pool sizes cannot
increase, the result is poor performance, with commands such as a simple 'ls'
taking 10-20 seconds to complete.  The group lookup cannot be cached because
there is no further space to hold the data.

Certainly it is possible to work around this problem by increasing
'suggested-size' from say 211 to 10007, but clearly the 'mremap' is going to
fail in any case.

Can we not use malloc and realloc instead ?

-- 
           Summary: nscd cannot extend memory heap sizes
           Product: glibc
           Version: 2.3.5
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nscd
        AssignedTo: drepper at redhat dot com
        ReportedBy: nick at sqrt dot co dot uk
                CC: glibc-bugs at sources dot redhat dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://sources.redhat.com/bugzilla/show_bug.cgi?id=1204

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