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    SubjectRe: [RFC PATCH 0/4] Gang scheduling in CFS

    * Nikunj A Dadhania <nikunj@linux.vnet.ibm.com> wrote:

    > Here some interesting perf reports from inside the guest:
    >
    > Baseline:
    > 29.79% ebizzy [kernel.kallsyms] [k] native_flush_tlb_others
    > 18.70% ebizzy libc-2.12.so [.] __GI_memcpy
    > 7.23% ebizzy [kernel.kallsyms] [k] get_page_from_freelist
    > 5.38% ebizzy [kernel.kallsyms] [k] __do_page_fault
    > 4.50% ebizzy [kernel.kallsyms] [k] ____pagevec_lru_add
    > 3.58% ebizzy [kernel.kallsyms] [k] default_send_IPI_mask_logical
    > 3.26% ebizzy [kernel.kallsyms] [k] native_flush_tlb_single
    > 2.82% ebizzy [kernel.kallsyms] [k] handle_pte_fault
    > 2.16% ebizzy [kernel.kallsyms] [k] kunmap_atomic
    > 2.10% ebizzy [kernel.kallsyms] [k] _spin_unlock_irqrestore
    > 1.90% ebizzy [kernel.kallsyms] [k] down_read_trylock
    > 1.65% ebizzy [kernel.kallsyms] [k] __mem_cgroup_commit_charge.clone.4
    > 1.60% ebizzy [kernel.kallsyms] [k] up_read
    > 1.24% ebizzy [kernel.kallsyms] [k] __alloc_pages_nodemask
    >
    > Gang:
    > 22.53% ebizzy libc-2.12.so [.] __GI_memcpy
    > 9.73% ebizzy [kernel.kallsyms] [k] ____pagevec_lru_add
    > 8.22% ebizzy [kernel.kallsyms] [k] get_page_from_freelist
    > 7.80% ebizzy [kernel.kallsyms] [k] default_send_IPI_mask_logical
    > 7.68% ebizzy [kernel.kallsyms] [k] native_flush_tlb_others
    > 6.22% ebizzy [kernel.kallsyms] [k] __do_page_fault
    > 5.54% ebizzy [kernel.kallsyms] [k] native_flush_tlb_single
    > 4.44% ebizzy [kernel.kallsyms] [k] _spin_unlock_irqrestore
    > 2.90% ebizzy [kernel.kallsyms] [k] kunmap_atomic
    > 2.78% ebizzy [kernel.kallsyms] [k] __mem_cgroup_commit_charge.clone.4
    > 2.76% ebizzy [kernel.kallsyms] [k] handle_pte_fault
    > 2.16% ebizzy [kernel.kallsyms] [k] __mem_cgroup_uncharge_common
    > 1.59% ebizzy [kernel.kallsyms] [k] down_read_trylock
    > 1.43% ebizzy [kernel.kallsyms] [k] up_read
    >
    > I see the main difference between both the reports is:
    > native_flush_tlb_others.

    So it would be important to figure out why ebizzy gets into so
    many TLB flushes and why gang scheduling makes it go away.

    Thanks,

    Ingo


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