Re: [patch] HT scheduler, sched-2.5.68-A9

From: Martin J. Bligh (mbligh@aracnet.com)
Date: Tue Apr 22 2003 - 18:48:43 EST


> the attached patch (against 2.5.68 or BK-curr) is the latest
> implementation of the "no compromises" HT-scheduler. I fixed a couple of
> bugs, and the scheduler is now stable and behaves properly on a
> 2-CPU-2-sibling HT testbox. The patch can also be downloaded from:
>
> http://redhat.com/~mingo/O(1)-scheduler/
>
> bug reports, suggestions welcome,

Hmmm. When the machine is loaded up fully, this seems OK, but for lower
loads, it seems to have a significant degredation. This is on my normal
16-way machine, no HT at all ... just checking for degredations. At a
guess, maybe it's bouncing stuff around between runqueues under low
loads?

Are there things embedded in here that change stuff for non-HT machines?

M.

DISCLAIMER: SPEC(tm) and the benchmark name SDET(tm) are registered
trademarks of the Standard Performance Evaluation Corporation. This
benchmarking was performed for research purposes only, and the run results
are non-compliant and not-comparable with any published results.

Results are shown as percentages of the first set displayed

SDET 1 (see disclaimer)
                           Throughput Std. Dev
                   2.5.68 100.0% 0.7%
                2.5.68-ht 72.9% 1.8%

SDET 2 (see disclaimer)
                           Throughput Std. Dev
                   2.5.68 100.0% 2.8%
                2.5.68-ht 73.7% 2.1%

SDET 4 (see disclaimer)
                           Throughput Std. Dev
                   2.5.68 100.0% 1.0%
                2.5.68-ht 62.5% 47.0%

SDET 8 (see disclaimer)
                           Throughput Std. Dev
                   2.5.68 100.0% 0.6%
                2.5.68-ht 92.6% 1.0%

SDET 16 (see disclaimer)
                           Throughput Std. Dev
                   2.5.68 100.0% 0.1%
                2.5.68-ht 100.0% 0.5%

SDET 32 (see disclaimer)
                           Throughput Std. Dev
                   2.5.68 100.0% 0.4%
                2.5.68-ht 99.1% 0.6%

SDET 64 (see disclaimer)
                           Throughput Std. Dev
                   2.5.68 100.0% 0.2%
                2.5.68-ht 99.0% 0.1%

SDET 128 (see disclaimer)
                           Throughput Std. Dev
                   2.5.68 100.0% 0.1%
                2.5.68-ht 99.0% 0.1%

diffprofile for SDET 4:

     12339 28.7% total
     10551 27.0% default_idle
       313 75.6% page_add_rmap
       240 110.1% copy_page_range
       192 243.0% do_wp_page
       174 31.1% page_remove_rmap
        51 20.6% zap_pte_range
        48 65.8% do_anonymous_page
        48 41.0% find_get_page
        48 160.0% copy_mm
        41 41.4% __d_lookup
        38 44.7% __copy_to_user_ll
        34 82.9% __copy_user_intel
        32 110.3% copy_process
        28 28.9% release_pages
        27 158.8% current_kernel_time
        23 121.1% release_task
        23 35.4% kmem_cache_free
        20 125.0% free_hot_cold_page
        17 77.3% buffered_rmqueue
        15 100.0% __copy_from_user_ll
        15 24.2% do_no_page
        13 16.9% do_page_fault
        12 44.4% pte_alloc_one
        12 57.1% schedule
        12 400.0% copy_files
        11 73.3% exit_notify
        10 29.4% path_lookup
         9 180.0% dup_task_struct
         9 27.3% atomic_dec_and_lock
         7 31.8% handle_mm_fault
         7 140.0% block_invalidatepage
         7 38.9% __pte_chain_free
         7 14.0% clear_page_tables
         7 116.7% fd_install
         7 77.8% write_profile
         7 350.0% generic_delete_inode
         6 54.5% ext2_update_inode
         6 60.0% do_page_cache_readahead
         6 66.7% dentry_open

Which looks like maybe more off-node NUMA accesses in there ...
is there some new rebalance mechanism that could be bouncing
stuff across nodes?

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