• Steven Whitehouse's avatar
    GFS2: Metadata address space clean up · 009d8518
    Steven Whitehouse authored
    Since the start of GFS2, an "extra" inode has been used to store
    the metadata belonging to each inode. The only reason for using
    this inode was to have an extra address space, the other fields
    were unused. This means that the memory usage was rather inefficient.
    
    The reason for keeping each inode's metadata in a separate address
    space is that when glocks are requested on remote nodes, we need to
    be able to efficiently locate the data and metadata which relating
    to that glock (inode) in order to sync or sync and invalidate it
    (depending on the remotely requested lock mode).
    
    This patch adds a new type of glock, which has in addition to
    its normal fields, has an address space. This applies to all
    inode and rgrp glocks (but to no other glock types which remain
    as before). As a result, we no longer need to have the second
    inode.
    
    This results in three major improvements:
     1. A saving of approx 25% of memory used in caching inodes
     2. A removal of the circular dependency between inodes and glocks
     3. No confusion between "normal" and "metadata" inodes in super.c
    
    Although the first of these is the more immediately apparent, the
    second is just as important as it now enables a number of clean
    ups at umount time. Those will be the subject of future patches.
    Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
    009d8518
main.c 4.83 KB