Messages in this thread | | | Date | Wed, 23 Feb 2022 15:35:35 +0530 | Subject | Re: [PATCH][RFC] sched: Stop searching for idle cpu if the LLC domain is overloaded | From | K Prateek Nayak <> |
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Hello Chenyu,
On 2/7/2022 9:10 AM, Chen Yu wrote: > [Problem Statement] > Searching for an idle cpu/core in a LLC domain is time consuming > when the LLC domain is relatively busy. Even worse, it is possible > that after iterating the whole LLC domain, it might still > fail to find an idle cpu/core.
We tested the patch running some standard benchmark on a dual socket AMD Zen3 system (2 x 64C/128T). Following are the results comparing the results seen on tip/sched/core (sched-tip) and tip/sched/core + this patch (util-avg)
~~~~~~~~~ hackbench ~~~~~~~~~
NPS Mode - NPS1 Test: sched-tip util-avg 1-groups: 4.97 (0.00 pct) 5.06 (-1.81 pct) 2-groups: 5.71 (0.00 pct) 5.65 (1.05 pct) 4-groups: 6.33 (0.00 pct) 6.22 (1.73 pct) 8-groups: 7.93 (0.00 pct) 7.77 (2.01 pct) 16-groups: 12.35 (0.00 pct) 11.75 (4.85 pct)
NPS Mode - NPS2 Test: sched-tip util-avg 1-groups: 4.87 (0.00 pct) 4.97 (-2.05 pct) 2-groups: 5.43 (0.00 pct) 5.39 (0.73 pct) 4-groups: 6.07 (0.00 pct) 5.94 (2.14 pct) 8-groups: 7.46 (0.00 pct) 7.39 (0.93 pct) 16-groups: 10.27 (0.00 pct) 10.07 (1.94 pct)
NPS Mode - NPS4 Test: sched-tip util-avg 1-groups: 4.87 (0.00 pct) 4.89 (-0.41 pct) 2-groups: 5.40 (0.00 pct) 5.48 (-1.48 pct) 4-groups: 6.15 (0.00 pct) 6.17 (-0.32 pct) 8-groups: 7.63 (0.00 pct) 7.53 (1.31 pct) 16-groups: 10.24 (0.00 pct) 9.89 (3.41 pct)
~~~~~~~~ schbench ~~~~~~~~
NPS Mode - NPS1 #workers: sched-tip util-avg 1: 13.00 (0.00 pct) 14.50 (-11.53 pct) 2: 31.50 (0.00 pct) 34.00 (-7.93 pct) 4: 43.50 (0.00 pct) 37.50 (13.79 pct) 8: 56.00 (0.00 pct) 50.50 (9.82 pct) 16: 69.50 (0.00 pct) 68.50 (1.43 pct) 32: 107.00 (0.00 pct) 106.50 (0.46 pct) 64: 191.00 (0.00 pct) 191.50 (-0.26 pct) 128: 413.50 (0.00 pct) 408.50 (1.20 pct) 256: 950.00 (0.00 pct) 947.00 (0.31 pct) 512: 60352.00 (0.00 pct) 60288.00 (0.10 pct)
NPS Mode - NPS2 #workers: sched-tip util-avg 1: 11.50 (0.00 pct) 11.00 (4.34 pct) 2: 26.00 (0.00 pct) 30.00 (-15.38 pct) 4: 36.00 (0.00 pct) 39.00 (-8.33 pct) 8: 57.50 (0.00 pct) 49.50 (13.91 pct) 16: 68.50 (0.00 pct) 69.00 (-0.72 pct) 32: 105.50 (0.00 pct) 104.50 (0.94 pct) 64: 192.50 (0.00 pct) 189.50 (1.55 pct) 128: 403.50 (0.00 pct) 430.00 (-6.56 pct) 256: 945.00 (0.00 pct) 957.00 (-1.26 pct) 512: 60288.00 (0.00 pct) 60224.00 (0.10 pct)
NPS Mode - NPS4 #workers: sched-tip util-avg 1: 12.50 (0.00 pct) 11.50 (8.00 pct) 2: 29.00 (0.00 pct) 23.00 (20.68 pct) 4: 28.50 (0.00 pct) 29.50 (-3.50 pct) 8: 45.00 (0.00 pct) 46.50 (-3.33 pct) 16: 74.00 (0.00 pct) 84.00 (-13.51 pct) 32: 110.50 (0.00 pct) 108.50 (1.80 pct) 64: 198.00 (0.00 pct) 191.50 (3.28 pct) 128: 434.00 (0.00 pct) 418.00 (3.68 pct) 256: 964.00 (0.00 pct) 952.00 (1.24 pct) 512: 60352.00 (0.00 pct) 60352.00 (0.00 pct)
~~~~~~ tbench ~~~~~~
NPS Mode - NPS1 Clients: sched-tip util-avg 1 475.40 (0.00 pct) 480.46 (1.06 pct) 2 939.62 (0.00 pct) 929.13 (-1.11 pct) 4 1767.75 (0.00 pct) 1798.94 (1.76 pct) 8 3315.70 (0.00 pct) 3231.78 (-2.53 pct) 16 5887.79 (0.00 pct) 6037.36 (2.54 pct) 32 10202.20 (0.00 pct) 10223.65 (0.21 pct) 64 16816.42 (0.00 pct) 17122.40 (1.81 pct) 128 28423.90 (0.00 pct) 28680.46 (0.90 pct) 256 26726.29 (0.00 pct) 52502.83 (96.44 pct) 512 53082.43 (0.00 pct) 53635.54 (1.04 pct) 1024 52940.64 (0.00 pct) 53051.05 (0.20 pct)
NPS Mode - NPS2 Clients: sched-tip util-avg 1 481.84 (0.00 pct) 479.67 (-0.45 pct) 2 941.13 (0.00 pct) 927.93 (-1.40 pct) 4 1797.61 (0.00 pct) 1770.86 (-1.48 pct) 8 3353.37 (0.00 pct) 3360.29 (0.20 pct) 16 5779.49 (0.00 pct) 5925.27 (2.52 pct) 32 10810.27 (0.00 pct) 10855.17 (0.41 pct) 64 17046.83 (0.00 pct) 17457.64 (2.40 pct) 128 28799.32 (0.00 pct) 28855.49 (0.19 pct) 256 27654.49 (0.00 pct) 47126.18 (70.41 pct) 512 51831.52 (0.00 pct) 51219.55 (-1.18 pct) 1024 52579.87 (0.00 pct) 50213.68 (-4.50 pct)
NPS Mode - NPS4 Clients: sched-tip util-avg 1 474.08 (0.00 pct) 478.40 (0.91 pct) 2 928.23 (0.00 pct) 937.76 (1.02 pct) 4 1754.78 (0.00 pct) 1741.17 (-0.77 pct) 8 3219.31 (0.00 pct) 3318.00 (3.06 pct) 16 5791.53 (0.00 pct) 5687.78 (-1.79 pct) 32 9810.76 (0.00 pct) 10866.32 (10.75 pct) 64 17098.46 (0.00 pct) 17203.60 (0.61 pct) 128 28575.94 (0.00 pct) 28020.97 (-1.94 pct) 256 25997.38 (0.00 pct) 47735.83 (83.61 pct) 512 47698.94 (0.00 pct) 48220.54 (1.09 pct) 1024 51451.30 (0.00 pct) 50455.47 (-1.93 pct)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Stream with 16 threads. built with -DSTREAM_ARRAY_SIZE=128000000, -DNTIMES=10 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NPS Mode - NPS1 Test: sched-tip util-avg Copy: 175278.66 (0.00 pct) 147847.67 (-15.64 pct) Scale: 193235.46 (0.00 pct) 186582.76 (-3.44 pct) Add: 220232.14 (0.00 pct) 208519.22 (-5.31 pct) Triad: 215526.78 (0.00 pct) 204975.14 (-4.89 pct)
NPS Mode - NPS2 Test: sched-tip util-avg Copy: 166600.09 (0.00 pct) 146456.45 (-12.09 pct) Scale: 190820.84 (0.00 pct) 179603.16 (-5.87 pct) Add: 214660.01 (0.00 pct) 198636.00 (-7.46 pct) Triad: 210879.10 (0.00 pct) 196132.74 (-6.99 pct)
NPS Mode - NPS4 Test: sched-tip util-avg Copy: 173888.83 (0.00 pct) 180948.16 (4.05 pct) Scale: 193027.03 (0.00 pct) 199330.65 (3.26 pct) Add: 218731.48 (0.00 pct) 221743.63 (1.37 pct) Triad: 214651.06 (0.00 pct) 218036.35 (1.57 pct)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Stream with 16 threads. built with -DSTREAM_ARRAY_SIZE=128000000, -DNTIMES=100 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NPS Mode - NPS1 Test: sched-tip util-avg Copy: 222954.79 (0.00 pct) 219066.70 (-1.74 pct) Scale: 208255.97 (0.00 pct) 215060.20 (3.26 pct) Add: 247694.16 (0.00 pct) 262893.33 (6.13 pct) Triad: 236060.27 (0.00 pct) 250188.38 (5.98 pct)
NPS Mode - NPS2 Test: sched-tip util-avg Copy: 226147.92 (0.00 pct) 228438.70 (1.01 pct) Scale: 214059.09 (0.00 pct) 215959.36 (0.88 pct) Add: 264978.05 (0.00 pct) 270058.63 (1.91 pct) Triad: 253095.73 (0.00 pct) 257466.31 (1.72 pct)
NPS Mode - NPS4 Test: sched-tip util-avg Copy: 223484.37 (0.00 pct) 266929.80 (19.44 pct) Scale: 224198.90 (0.00 pct) 235316.80 (4.95 pct) Add: 272008.98 (0.00 pct) 294452.15 (8.25 pct) Triad: 258219.64 (0.00 pct) 285935.30 (10.73 pct) --
We see great results in case of tbench with 256 workers when the system is fully loaded which is exactly the kind of scenario this patch optimizes for. Hackbench too shows improvements, especially in the case of 16-groups. -- Thanks and Regards, Prateek
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