• Tejun Heo's avatar
    percpu, x86: don't use PMD_SIZE as embedded atom_size on 32bit · d5e28005
    Tejun Heo authored
    With the embed percpu first chunk allocator, x86 uses either PAGE_SIZE
    or PMD_SIZE for atom_size.  PMD_SIZE is used when CPU supports PSE so
    that percpu areas are aligned to PMD mappings and possibly allow using
    PMD mappings in vmalloc areas in the future.  Using larger atom_size
    doesn't waste actual memory; however, it does require larger vmalloc
    space allocation later on for !first chunks.
    
    With reasonably sized vmalloc area, PMD_SIZE shouldn't be a problem
    but x86_32 at this point is anything but reasonable in terms of
    address space and using larger atom_size reportedly leads to frequent
    percpu allocation failures on certain setups.
    
    As there is no reason to not use PMD_SIZE on x86_64 as vmalloc space
    is aplenty and most x86_64 configurations support PSE, fix the issue
    by always using PMD_SIZE on x86_64 and PAGE_SIZE on x86_32.
    
    v2: drop cpu_has_pse test and make x86_64 always use PMD_SIZE and
        x86_32 PAGE_SIZE as suggested by hpa.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Reported-by: default avatarYanmin Zhang <yanmin.zhang@intel.com>
    Reported-by: default avatarShuoX Liu <shuox.liu@intel.com>
    Acked-by: default avatarH. Peter Anvin <hpa@zytor.com>
    LKML-Reference: <4F97BA98.6010001@intel.com>
    Cc: stable@vger.kernel.org
    d5e28005
setup_percpu.c 7.92 KB