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    mm, x86: Revisit tlb_flushall_shift tuning for page flushes except on IvyBridge · b9a3b4c9
    Mel Gorman 提交于
    There was a large ebizzy performance regression that was
    bisected to commit 611ae8e3 (x86/tlb: enable tlb flush range
    support for x86).  The problem was related to the
    tlb_flushall_shift tuning for IvyBridge which was altered.  The
    problem is that it is not clear if the tuning values for each
    CPU family is correct as the methodology used to tune the values
    is unclear.
    
    This patch uses a conservative tlb_flushall_shift value for all
    CPU families except IvyBridge so the decision can be revisited
    if any regression is found as a result of this change.
    IvyBridge is an exception as testing with one methodology
    determined that the value of 2 is acceptable.  Details are in
    the changelog for the patch "x86: mm: Change tlb_flushall_shift
    for IvyBridge".
    
    One important aspect of this to watch out for is Xen.  The
    original commit log mentioned large performance gains on Xen.
    It's possible Xen is more sensitive to this value if it flushes
    small ranges of pages more frequently than workloads on bare
    metal typically do.
    Signed-off-by: NMel Gorman <mgorman@suse.de>
    Tested-by: NDavidlohr Bueso <davidlohr@hp.com>
    Reviewed-by: NRik van Riel <riel@redhat.com>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Cc: Alex Shi <alex.shi@linaro.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Link: http://lkml.kernel.org/n/tip-dyzMww3fqugnhbhgo6Gxmtkw@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
    b9a3b4c9
amd.c 22.3 KB