<div dir="ltr"><p class="MsoNormal" align="left" style="word-break:keep-all"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">Hi,</span><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span></span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">I have studied OVS in performance aspect.
And, I found out that flow masking and looking up table have quite overhead.<span></span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">I read a paper &#39; “The Design and
Implementation of Open vSwitch.” USENIX NSDI 2015&#39;, and discovered that there
is why use masking process in the paper. <span></span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">the paper said &quot;<b>While the
microflow cache works well with most traffic</b><span></span></span></p>

<p class="MsoNormal"><b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">patterns, it suffers serious performance
degradation when</span></b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span></span></span></p>

<p class="MsoNormal"><b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">faced with large numbers of short lived
connections. In</span></b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span></span></span></p>

<p class="MsoNormal"><b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">this case, many packets miss the cache,
and must not only</span></b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span></span></span></p>

<p class="MsoNormal"><b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">cross the kernel-userspace boundary, but
also execute a</span></b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span></span></span></p>

<p class="MsoNormal"><b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">long series of expensive packet
classifications.</span></b><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">&quot;<span></span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">I have thought about it, and I have some
questions.<span></span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">1. If only microflow cache works and
there are many short lived connections, does it make many tuples in table, and
does it suffers serious performance degradation by the many tuples(very many
tuple makes context switching to Userlevel)?<span></span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">2. I know that OVS uses hash for table
index. if only microflow cache and there are small amount of entries in the
table, is it possible to find entry in O(1) time?<span></span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">3. In paper, microflow and megaflow use
the word &#39;cache&#39;. However, when I open the OVS code, it looks like they are in
main memory area. doesn&#39;t the &#39;cache&#39; mean hardware cache?<span></span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">please let me know if you have some
insights.<span></span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif"><span> </span></span></p>

<p class="MsoNormal"><span lang="EN-US" style="font-size:12pt;font-family:굴림,sans-serif">Thanks!<span></span></span></p></div>