• Tejun Heo's avatar
    x86: implement percpu_alloc kernel parameter · fa8a7094
    Tejun Heo authored
    According to Andi, it isn't clear whether lpage allocator is worth the
    trouble as there are many processors where PMD TLB is far scarcer than
    PTE TLB.  The advantage or disadvantage probably depends on the actual
    size of percpu area and specific processor.  As performance
    degradation due to TLB pressure tends to be highly workload specific
    and subtle, it is difficult to decide which way to go without more
    data.
    
    This patch implements percpu_alloc kernel parameter to allow selecting
    which first chunk allocator to use to ease debugging and testing.
    
    While at it, make sure all the failure paths report why something
    failed to help determining why certain allocator isn't working.  Also,
    kill the "Great future plan" comment which had already been realized
    quite some time ago.
    
    [ Impact: allow explicit percpu first chunk allocator selection ]
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Reported-by: default avatarJan Beulich <JBeulich@novell.com>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: Ingo Molnar <mingo@elte.hu>
    fa8a7094
percpu.c 36.3 KB