hdf5_ep

[svn-r16290] Purpose: 

    Adding code to maintain a min_clean_fraction in the cache in serial mode.

Description:

    The metadata cache now has the ability to maintain a min_clean_fraction
    when in serial mode. The default initial cache size has been changed
    from 1MB to 2MB, and the default min_clean_fraction has been set at 30%.

    This check-in includes modifications to H5C.c to support maintaining a
    min_clean_size, including the addition of clean_index_size and 
    dirty_index_size trackers, modifications to the H5C_make_space_in_cache 
    algorithm, as well as associated test code and additional statistics 
    tracking variables.

    Maintaining the min_clean_fraction addresses the possibility of
    experiencing a "metadata blizzard" when the cache gets completely
    full with dirty entries. Upon having to make space, the cache would
    previously need to flush every single entry in the cache before coming
    across a clean entry which could be evicted. This resulted in unnecessary
    flushing of oftentimes hot entries in the cache. Maintaining the
    min_clean_fraction ensures that, when space is needed, clean entries
    are more readily available to evict.

Tested:

    jam, smirom, linew (h5committest)