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linux-kernel-module-cheat/bst-vs-heap-vs-hashmap.html
Ciro Santilli 8dfebecfa6 2b436adf36
2021-07-27 16:52:42 +01:00

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<title>Linux Kernel Module Cheat</title>
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</head>
<body id="bst-vs-heap-vs-hashmap" class="article">
<div id="header">
<h1>Linux Kernel Module Cheat</h1>
</div>
<div id="content">
<div class="sect3">
<h4 id="bst-vs-heap-vs-hashmap"><a class="anchor" href="#bst-vs-heap-vs-hashmap"></a><a class="link" href="#bst-vs-heap-vs-hashmap">27.8.1. BST vs heap vs hashmap</a></h4>
<div class="paragraph">
<p>TODO: move benchmark graph from <a href="https://github.com/cirosantilli/linux-kernel-module-cheat/blob/master/userland/cpp/bst_vs_heap_vs_hashmap.cpp">userland/cpp/bst_vs_heap_vs_hashmap.cpp</a> to <a href="https://github.com/cirosantilli/linux-kernel-module-cheat/blob/master/userland/algorithm/set">userland/algorithm/set</a>.</p>
</div>
<div class="paragraph">
<p>The following benchmark setup works both:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>on host through timers + <a href="https://stackoverflow.com/questions/51952471/why-do-i-get-a-constant-instead-of-logarithmic-curve-for-an-insert-time-benchmar/51953081#51953081">granule</a></p>
</li>
<li>
<p>gem5 with <a href="m5ops-instructions.html">dumpstats</a>, which can get more precise results with <code>granule == 1</code></p>
</li>
</ul>
</div>
<div class="paragraph">
<p>It has been used to answer:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>BST vs heap: <a href="https://stackoverflow.com/questions/6147243/heap-vs-binary-search-tree-bst/29548834#29548834" class="bare">https://stackoverflow.com/questions/6147243/heap-vs-binary-search-tree-bst/29548834#29548834</a></p>
</li>
<li>
<p><code>std::set</code>: <a href="https://stackoverflow.com/questions/2558153/what-is-the-underlying-data-structure-of-a-stl-set-in-c/51944661#51944661" class="bare">https://stackoverflow.com/questions/2558153/what-is-the-underlying-data-structure-of-a-stl-set-in-c/51944661#51944661</a></p>
</li>
<li>
<p><code>std::map</code>: <a href="https://stackoverflow.com/questions/18414579/what-data-structure-is-inside-stdmap-in-c/51945119#51945119" class="bare">https://stackoverflow.com/questions/18414579/what-data-structure-is-inside-stdmap-in-c/51945119#51945119</a></p>
</li>
</ul>
</div>
<div class="paragraph">
<p>To benchmark on the host, we do:</p>
</div>
<div class="literalblock">
<div class="content">
<pre>./build-userland-in-tree \
--force-rebuild \
--optimization-level 3 \
./userland/cpp/bst_vs_heap_vs_hashmap.cpp \
;
./userland/cpp/bst_vs_heap_vs_hashmap.out 10000000 10000 0 | tee bst_vs_heap_vs_hashmap.dat
gnuplot \
-e 'input_noext="bst_vs_heap_vs_hashmap"' \
-e 'heap_zoom_max=50' \
-e 'hashmap_zoom_max=400' \
./bst-vs-heap-vs-hashmap.gnuplot \
;
xdg-open bst_vs_heap_vs_hashmap.tmp.png</pre>
</div>
</div>
<div class="paragraph">
<p>The parameters <code>heap_zoom_max</code> and <code>hashmap_zoom_max</code> are chosen manually interactively to best showcase the regions of interest in those plots.</p>
</div>
<div class="paragraph">
<p>To benchmark on gem5, we first build the benchmark with <a href="m5ops-instructions.html">m5ops instructions</a> enabled, and then we run it and extract the stats:</p>
</div>
<div class="literalblock">
<div class="content">
<pre>./build-userland \
--arch x86_64 \
--ccflags='-DLKMC_M5OPS_ENABLE=1' \
--force-rebuild userland/cpp/bst_vs_heap_vs_hashmap.cpp \
--optimization-level 3 \
;
./run \
--arch x86_64 \
--emulator gem5 \
--userland userland/cpp/bst_vs_heap_vs_hashmap.cpp \
--cli-args='100000 1 0' \
-- \
--cpu-type=DerivO3CPU \
--caches \
--l2cache \
--l1d_size=32kB \
--l1i_size=32kB \
--l2_size=256kB \
--l3_size=20MB \
;
./bst-vs-heap-vs-hashmap-gem5-stats --arch x86_64 | tee bst_vs_heap_vs_hashmap_gem5.dat
gnuplot \
-e 'input_noext="bst_vs_heap_vs_hashmap_gem5"' \
-e 'heap_zoom_max=500' \
-e 'hashmap_zoom_max=400' \
./bst-vs-heap-vs-hashmap.gnuplot \
;
xdg-open bst_vs_heap_vs_hashmap_gem5.tmp.png</pre>
</div>
</div>
<div class="paragraph">
<p>TODO: the gem5 simulation blows up on a tcmalloc allocation somewhere near 25k elements as of 3fdd83c2c58327d9714fa2347c724b78d7c05e2b + 1, likely linked to the extreme inefficiency of the stats collection?</p>
</div>
<div class="paragraph">
<p>The cache sizes were chosen to match the host <a href="p51.html">2017 Lenovo ThinkPad P51</a> to improve the comparison. Ideally we should also use the same standard library.</p>
</div>
<div class="paragraph">
<p>Note that this will take a long time, and will produce a humongous ~40Gb stats file as explained at: <a href="gem5-only-dump-selected-stats.html">Section 24.10.3.2, &#8220;gem5 only dump selected stats&#8221;</a></p>
</div>
<div class="paragraph">
<p>Sources:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><a href="https://github.com/cirosantilli/linux-kernel-module-cheat/blob/master/userland/cpp/bst_vs_heap_vs_hashmap.cpp">userland/cpp/bst_vs_heap_vs_hashmap.cpp</a></p>
</li>
<li>
<p><a href="https://github.com/cirosantilli/linux-kernel-module-cheat/blob/master/bst-vs-heap-vs-hashmap-gem5-stats">bst-vs-heap-vs-hashmap-gem5-stats</a></p>
</li>
<li>
<p><a href="https://github.com/cirosantilli/linux-kernel-module-cheat/blob/master/bst-vs-heap-vs-hashmap.gnuplot">bst-vs-heap-vs-hashmap.gnuplot</a></p>
</li>
</ul>
</div>
<div class="ulist">
<ul>
</ul>
</div>
</div>
<div class="paragraph nav-footer">
<p> Up: <a href="algorithms.html">Algorithms</a> | ⌂ Home: <a href="README.html">Linux Kernel Module Cheat</a> | Next: <a href="blas.html">BLAS</a> →</p>
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