Re: [Xen-devel] [PATCH v5 3/8] qspinlock, x86: Add x86 specific optimization for 2 contending tasks

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

Updated version, this includes numbers for my SNB desktop and Waiman's
variant.

Curiously Waiman's version seems consistently slower on 2 cross node
CPUs. Whereas my version seems to have a problem on SNB with 2 CPUs.

There's something weird with the ticket lock numbers; when I compile
the code with:

  gcc (Debian 4.7.2-5) 4.7.2

I get the first set; when I compile with:

  gcc (Ubuntu/Linaro 4.7.3-2ubuntu4) 4.7.3

I get the second set; afaict the other locks don't seem to have this
problem, but I only just noticed.

---

I measure the cycles spend in arch_spin_lock() + arch_spin_unlock().

The machines used are a 4 node (2 socket) AMD Interlagos, a 2 node
(2 socket) Intel Westmere-EP and my i7-2600K (SNB) desktop.


(ticket)                (qspinlock + all)       (waiman)


AMD Interlagos

Local:

 1:    324.425530        1:    324.102142        1:    323.857834
 2:  17141.324050        2:    620.185930        2:    618.737681
 3:  52212.232343        3:  25242.574661        3:  24888.154161
 4:  93136.458314        4:  47982.037866        4:  48227.610976
 6: 167967.455965        6:  95345.011864        6:  94372.276116
 8: 245402.534869        8: 142412.451438        8: 140516.525791

 1: 324.071515
 2: 981.778516
 3: 24414.144262
 4: 50868.376667
 6: 99536.890504
 8: 151616.395779

2 - nodes:

 2:  12763.640956        2:   1879.460823        2:   2023.594014
 4:  94423.027123        4:  48278.719130        4:  48621.724929
 6: 167903.698361        6:  96747.767310        6:  95815.242461
 8: 257243.508294        8: 144672.846317        8: 143282.222038

 2:   1875.637053
 4:  50082.796058
 6: 107780.361523
 8: 163166.728218

4 - nodes:

 4:  82408.853603        4:  49820.323075        4:  50566.036473
 8: 260492.952355        8: 143538.264724        8: 143485.584624
16: 630099.031148       16: 337796.553795       16: 333419.421338

 4: 55409.896671
 8: 167340.905593
16: 443195.057052



Intel WSM-EP

Local:

1:    19.002249         1:    29.002844         1:    28.979917
2:  5093.275530         2:  1282.209519         2:  1236.624785
3: 22300.859761         3: 22127.477388         3: 22336.241120
4: 44929.922325         4: 44493.881832         4: 44832.450598
6: 86338.755247         6: 86360.083940         6: 85808.603491

1: 20.009974
2: 1206.419074
3: 22071.535000
4: 44606.831373
6: 86498.760774

2 - nodes:

2:   1527.466159        2:   1227.051993        2:   1434.204666
4:  46004.232179        4:  46450.787234        4:  46999.356429
6:  89226.472057        6:  90124.984324        6:  90110.423115
8: 137225.472406        8: 137909.184358        8: 137988.290401


Intel SNB

Local:

1:    15.276759         1:    25.336807         1:    25.353041
2:   714.621152         2:   843.240641         2:   711.281211
3: 11339.104267         3: 11751.159167         3: 11684.286334
4: 22648.387376         4: 23454.798068         4: 22903.498910

Attachment: spinlocks.tar.bz2
Description: Binary data

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