• Borislav Petkov's avatar
    x86, amd: Avoid cache aliasing penalties on AMD family 15h · dfb09f9b
    Borislav Petkov authored
    This patch provides performance tuning for the "Bulldozer" CPU. With its
    shared instruction cache there is a chance of generating an excessive
    number of cache cross-invalidates when running specific workloads on the
    cores of a compute module.
    
    This excessive amount of cross-invalidations can be observed if cache
    lines backed by shared physical memory alias in bits [14:12] of their
    virtual addresses, as those bits are used for the index generation.
    
    This patch addresses the issue by clearing all the bits in the [14:12]
    slice of the file mapping's virtual address at generation time, thus
    forcing those bits the same for all mappings of a single shared library
    across processes and, in doing so, avoids instruction cache aliases.
    
    It also adds the command line option "align_va_addr=(32|64|on|off)" with
    which virtual address alignment can be enabled for 32-bit or 64-bit x86
    individually, or both, or be completely disabled.
    
    This change leaves virtual region address allocation on other families
    and/or vendors unaffected.
    Signed-off-by: default avatarBorislav Petkov <borislav.petkov@amd.com>
    Link: http://lkml.kernel.org/r/1312550110-24160-2-git-send-email-bp@amd64.orgSigned-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
    dfb09f9b
amd.c 18.5 KB