• Christoph Lameter's avatar
    x86: 64-bit, make sparsemem vmemmap the only memory model · b263295d
    Christoph Lameter authored
    Use sparsemem as the only memory model for UP, SMP and NUMA.  Measurements
    indicate that DISCONTIGMEM has a higher overhead than sparsemem.  And
    FLATMEMs benefits are minimal.  So I think its best to simply standardize
    on sparsemem.
    
    Results of page allocator tests (test can be had via git from slab git
    tree branch tests)
    
    Measurements in cycle counts. 1000 allocations were performed and then the
    average cycle count was calculated.
    
    Order	FlatMem	Discontig	SparseMem
    0	  639	  665		  641
    1	  567	  647		  593
    2	  679	  774		  692
    3	  763	  967		  781
    4	  961	 1501		  962
    5	 1356	 2344		 1392
    6	 2224	 3982		 2336
    7	 4869	 7225		 5074
    8	12500	14048		12732
    9	27926	28223		28165
    10	58578	58714		58682
    
    (Note that FlatMem is an SMP config and the rest NUMA configurations)
    
    Memory use:
    
    SMP Sparsemem
    -------------
    
    Kernel size:
    
       text    data     bss     dec     hex filename
    3849268  397739 1264856 5511863  541ab7 vmlinux
    
                 total       used       free     shared    buffers     cached
    Mem:       8242252      41164    8201088          0        352      11512
    -/+ buffers/cache:      29300    8212952
    Swap:      9775512          0    9775512
    
    SMP Flatmem
    -----------
    
    Kernel size:
    
       text    data     bss     dec     hex filename
    3844612  397739 1264536 5506887  540747 vmlinux
    
    So 4.5k growth in text size vs. FLATMEM.
    
                 total       used       free     shared    buffers     cached
    Mem:       8244052      40544    8203508          0        352      11484
    -/+ buffers/cache:      28708    8215344
    
    2k growth in overall memory use after boot.
    
    NUMA discontig:
    
       text    data     bss     dec     hex filename
    3888124  470659 1276504 5635287  55fcd7 vmlinux
    
                 total       used       free     shared    buffers     cached
    Mem:       8256256      56908    8199348          0        352      11496
    -/+ buffers/cache:      45060    8211196
    Swap:      9775512          0    9775512
    
    NUMA sparse:
    
       text    data     bss     dec     hex filename
    3896428  470659 1276824 5643911  561e87 vmlinux
    
    8k text growth. Given that we fully inline virt_to_page and friends now
    that is rather good.
    
                 total       used       free     shared    buffers     cached
    Mem:       8264720      57240    8207480          0        352      11516
    -/+ buffers/cache:      45372    8219348
    Swap:      9775512          0    9775512
    
    The total available memory is increased by 8k.
    
    This patch makes sparsemem the default and removes discontig and
    flatmem support from x86.
    
    [ akpm@linux-foundation.org: allnoconfig build fix ]
    Acked-by: default avatarAndi Kleen <ak@suse.de>
    Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    b263295d
Kconfig 51.8 KB