• Matt Mackall's avatar
    [PATCH] slob: introduce the SLOB allocator · 10cef602
    Matt Mackall authored
    
    
    configurable replacement for slab allocator
    
    This adds a CONFIG_SLAB option under CONFIG_EMBEDDED.  When CONFIG_SLAB is
    disabled, the kernel falls back to using the 'SLOB' allocator.
    
    SLOB is a traditional K&R/UNIX allocator with a SLAB emulation layer,
    similar to the original Linux kmalloc allocator that SLAB replaced.  It's
    signicantly smaller code and is more memory efficient.  But like all
    similar allocators, it scales poorly and suffers from fragmentation more
    than SLAB, so it's only appropriate for small systems.
    
    It's been tested extensively in the Linux-tiny tree.  I've also
    stress-tested it with make -j 8 compiles on a 3G SMP+PREEMPT box (not
    recommended).
    
    Here's a comparison for otherwise identical builds, showing SLOB saving
    nearly half a megabyte of RAM:
    
    $ size vmlinux*
       text    data     bss     dec     hex filename
    3336372  529360  190812 4056544  3de5e0 vmlinux-slab
    3323208  527948  190684 4041840  3dac70 vmlinux-slob
    
    $ size mm/{slab,slob}.o
       text    data     bss     dec     hex filename
      13221     752      48   14021    36c5 mm/slab.o
       1896      52       8    1956     7a4 mm/slob.o
    
    /proc/meminfo:
                      SLAB          SLOB      delta
    MemTotal:        27964 kB      27980 kB     +16 kB
    MemFree:         24596 kB      25092 kB    +496 kB
    Buffers:            36 kB         36 kB       0 kB
    Cached:           1188 kB       1188 kB       0 kB
    SwapCached:          0 kB          0 kB       0 kB
    Active:            608 kB        600 kB      -8 kB
    Inactive:          808 kB        812 kB      +4 kB
    HighTotal:           0 kB          0 kB       0 kB
    HighFree:            0 kB          0 kB       0 kB
    LowTotal:        27964 kB      27980 kB     +16 kB
    LowFree:         24596 kB      25092 kB    +496 kB
    SwapTotal:           0 kB          0 kB       0 kB
    SwapFree:            0 kB          0 kB       0 kB
    Dirty:               4 kB         12 kB      +8 kB
    Writeback:           0 kB          0 kB       0 kB
    Mapped:            560 kB        556 kB      -4 kB
    Slab:             1756 kB          0 kB   -1756 kB
    CommitLimit:     13980 kB      13988 kB      +8 kB
    Committed_AS:     4208 kB       4208 kB       0 kB
    PageTables:         28 kB         28 kB       0 kB
    VmallocTotal:  1007312 kB    1007312 kB       0 kB
    VmallocUsed:        48 kB         48 kB       0 kB
    VmallocChunk:  1007264 kB    1007264 kB       0 kB
    
    (this work has been sponsored in part by CELF)
    
    From: Ingo Molnar <mingo@elte.hu>
    
       Fix 32-bitness bugs in mm/slob.c.
    
    Signed-off-by: default avatarMatt Mackall <mpm@selenic.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    10cef602