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    Subjectkernbench on 512p
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    I set out to benchmark the page cache round robin stuff I posted earlier to 
    see whether round robining across 256 nodes would really hurt kernbench
    performance. What I found was that things aren't scaling well enough to make
    reasonable measurements.

    time user system %cpu ctx sleeps
    2.6.8.1-mm1+nodespan 108.622 1588 10536 11158 31193 397966
    2.6.8.1-mm1+ns+rr 105.614 1163 8631 9302 27774 420888

    2.6.8.1-mm1+nodespan is just 2.6.8.1-mm1 with my last node-span patch applied.
    2.6.8.1-mm1+ns+rr is that plus the page cache round robin patch I posted
    recently. I just extracted the 'optimal run' average for each of the above
    lines.

    Here's the kernel profile. It would be nice if the patch to show which lock
    is contended got included. I think it was discussed awhile back, but I don't
    have one against the newly merged profiling code.

    [root@ascender root]# readprofile -m System.map | sort -nr | head -30
    208218076 total 30.1677
    90036167 ia64_pal_call_static 468938.3698
    88140492 default_idle 229532.5312
    10312592 ia64_save_scratch_fpregs 161134.2500
    10306777 ia64_load_scratch_fpregs 161043.3906
    8723555 ia64_spinlock_contention 90870.3646
    121385 rcu_check_quiescent_state 316.1068
    40464 file_move 180.6429
    32374 file_kill 144.5268
    25316 atomic_dec_and_lock 98.8906
    24814 clear_page 155.0875
    17709 file_ra_state_init 110.6813
    17603 clear_page_tables 13.4169
    16822 copy_page 65.7109
    16683 del_timer_sync 32.5840
    15098 zap_pte_range 7.8635
    15076 __d_lookup 16.8259
    13275 find_get_page 31.9111
    12898 __copy_user 5.5214
    10472 finish_task_switch 36.3611
    10037 ia64_pfn_valid 52.2760
    8610 get_zone_counts 22.4219
    7905 current_kernel_time 41.1719
    7155 __down_trylock 22.3594
    7063 _pagebuf_find 4.9049
    6995 xfs_ilock 13.6621
    6965 tasklet_action 8.3714
    6494 free_page_and_swap_cache 28.9911
    5652 nr_free_pages 22.0781
    5555 xfs_trans_push_ail 3.6165

    This is a 64p profile only. If I set the prof_cpu_mask to include all 512
    CPUs, the system livelocks. I reset the counter right after the warmup run,
    partly through the half load run, and collected it after a few runs were
    complete.

    Thanks,
    Jesse
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