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#epoll

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Felix Palmen :freebsd: :c64:<p>The next release of <a href="https://mastodon.bsd.cafe/tags/swad" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>swad</span></a> will probably bring not a single new feature, but focus on improvements, especially regarding <a href="https://mastodon.bsd.cafe/tags/performance" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>performance</span></a>. Support for using <a href="https://mastodon.bsd.cafe/tags/kqueue" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>kqueue</span></a> (<a href="https://mastodon.bsd.cafe/tags/FreeBSD" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>FreeBSD</span></a> et al) to handle <a href="https://mastodon.bsd.cafe/tags/signals" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>signals</span></a> is a part of it (which is done and works). Still unsure whether I'll also add support for <a href="https://mastodon.bsd.cafe/tags/Linux" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Linux</span></a>' <a href="https://mastodon.bsd.cafe/tags/signalfd" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>signalfd</span></a>. Using kqueue also as a better backend for <a href="https://mastodon.bsd.cafe/tags/timers" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>timers</span></a> is on the list.</p><p>Another hopefully quite relevant change is here:</p><p><a href="https://github.com/Zirias/poser/commit/798f23547295f89fa0c751f0e707c3474b5c689c" rel="nofollow noopener noreferrer" translate="no" target="_blank"><span class="invisible">https://</span><span class="ellipsis">github.com/Zirias/poser/commit</span><span class="invisible">/798f23547295f89fa0c751f0e707c3474b5c689c</span></a></p><p>In short, so far my <a href="https://mastodon.bsd.cafe/tags/poser" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>poser</span></a> lib was always awaiting readiness notification (from kqueue, or <a href="https://mastodon.bsd.cafe/tags/epoll" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>epoll</span></a> on Linux, or select/poll for other platforms) before doing any read or write on a socket. This is the ideal approach for reads, because in the common case, a socket is NOT ready for reading ... our kernel must have received something from the remote end first. But for writes, it's not so ideal. The common case is that a socket IS ready to write (because there's space left in the kernel's send buffers). So, just try it, and only register for notifications if it ever fails, makes more sense. Avoids pointless waiting and pointless events, and e.g. with epoll, even unnecessary syscalls. 😉</p>
Felix Palmen :freebsd: :c64:<p>Still working on <a href="https://mastodon.bsd.cafe/tags/swad" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>swad</span></a>, and currently very busy with improving quality, most of the actual work done inside my <a href="https://mastodon.bsd.cafe/tags/poser" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>poser</span></a> library.</p><p>After finally supporting <a href="https://mastodon.bsd.cafe/tags/kqueue" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>kqueue</span></a> and <a href="https://mastodon.bsd.cafe/tags/epoll" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>epoll</span></a>, I now integrated <a href="https://mastodon.bsd.cafe/tags/xxhash" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>xxhash</span></a> to completely replace my previous stupid and naive hashing. I also added a more involved <a href="https://mastodon.bsd.cafe/tags/dictionary" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>dictionary</span></a> class as an alternative to the already existing <a href="https://mastodon.bsd.cafe/tags/hashtable" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>hashtable</span></a>. While the hashtable's size must be pre-configured and collissions are only ever resolved by storing linked lists, the new dictionary dynamically nests multiple hashtables (using different bits of a single hash value). I hope to achieve acceptable scaling while maintaining also acceptable memory overhead that way ...</p><p><a href="https://mastodon.bsd.cafe/tags/swad" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>swad</span></a> already uses both container classes as appropriate.</p><p>Next I'll probably revisit poser's <a href="https://mastodon.bsd.cafe/tags/threadpool" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>threadpool</span></a>. I think I could replace <a href="https://mastodon.bsd.cafe/tags/pthread" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>pthread</span></a> condition variables by "simple" <a href="https://mastodon.bsd.cafe/tags/semaphores" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>semaphores</span></a>, which should also reduce overhead ... </p><p><a href="https://github.com/Zirias/swad" rel="nofollow noopener noreferrer" translate="no" target="_blank"><span class="invisible">https://</span><span class="">github.com/Zirias/swad</span><span class="invisible"></span></a></p><p><a href="https://mastodon.bsd.cafe/tags/c" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>c</span></a> <a href="https://mastodon.bsd.cafe/tags/coding" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>coding</span></a></p>
Felix Palmen :freebsd: :c64:<p>First change since <a href="https://mastodon.bsd.cafe/tags/swad" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>swad</span></a> 0.2 will actually be a (huge?) improvement to my <a href="https://mastodon.bsd.cafe/tags/poser" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>poser</span></a> lib. So far, it was hardwired to use the good old <a href="https://mastodon.bsd.cafe/tags/POSIX" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>POSIX</span></a> <a href="https://mastodon.bsd.cafe/tags/select" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>select</span></a> call. This is perfectly fine for handling around up to 100 (or at least less than 1000, YMMV) clients.</p><p>Some <a href="https://mastodon.bsd.cafe/tags/select" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>select</span></a> implementations offer defining the upper limit for checked file descriptors. Added support for that.</p><p>POSIX also specifies <a href="https://mastodon.bsd.cafe/tags/poll" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>poll</span></a>, which has very similar <a href="https://mastodon.bsd.cafe/tags/scalability" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>scalability</span></a> issues, but slightly different. Added support for this as well.</p><p>And then, I went on to add support for the <a href="https://mastodon.bsd.cafe/tags/Linux" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Linux</span></a>-specific <a href="https://mastodon.bsd.cafe/tags/epoll" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>epoll</span></a> and <a href="https://mastodon.bsd.cafe/tags/BSD" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>BSD</span></a>-specific <a href="https://mastodon.bsd.cafe/tags/kqueue" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>kqueue</span></a> (<a href="https://mastodon.bsd.cafe/tags/FreeBSD" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>FreeBSD</span></a>, <a href="https://mastodon.bsd.cafe/tags/NetBSD" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>NetBSD</span></a>, <a href="https://mastodon.bsd.cafe/tags/OpenBSD" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>OpenBSD</span></a>, ...) which are both designed to *solve* any scalability issues 🥳 </p><p>A little thing that slightly annoyed me about kqueue was that there's no support for temporarily changing the signal mask, so I had to do the silly dance shown in the screenshot. OTOH, it offers changing event filters and getting events in a single call, which I might try to even further optimize ... 😎</p><p><a href="https://mastodon.bsd.cafe/tags/C" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>C</span></a> <a href="https://mastodon.bsd.cafe/tags/coding" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>coding</span></a></p>
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