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#select

2 posts2 participants0 posts today
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Felix Palmen :freebsd: :c64:

First change since #swad 0.2 will actually be a (huge?) improvement to my #poser lib. So far, it was hardwired to use the good old #POSIX #select call. This is perfectly fine for handling around up to 100 (or at least less than 1000, YMMV) clients.

Some #select implementations offer defining the upper limit for checked file descriptors. Added support for that.

POSIX also specifies #poll, which has very similar #scalability issues, but slightly different. Added support for this as well.

And then, I went on to add support for the #Linux-specific #epoll and #BSD-specific #kqueue (#FreeBSD, #NetBSD, #OpenBSD, ...) which are both designed to *solve* any scalability issues 🥳

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 ... 😎

kqueue client code, manually relaxing the signal mask for just the single kevent() call waiting for new events.
#C#coding
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Dining & Cooking

New owner sought for MJ’s Gelato | Select diningandcooking.com/1965959/n #business #food #FoodTopics #news #select

Dining and Cooking · New owner sought for MJ’s Gelato | SelectMJ’s Gelato has been a staple of downtown Norfolk for the past couple of years, offering gelato and boba drinks while providing customers with a cozy spot to hang out and chill.In a Facebook post last month, current owners Steve and Karen Carlsen announced that they made the difficult decision to sell MJ’s and find someone to whom to hand over the reins of the shop.He explained that it was a family decision, with his oldest child going off to college, him having another job and his wife deciding that she couldn’t run it anymore. He said that finding a
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Felix Palmen :freebsd: :c64:

@toomanysecrets It's kind of funny the talk is all about #epoll although the text then correctly tells that BSD's (originally #FreeBSD but adopted by the others as well) #kqueue was the first async event interface without the scalability issues of #select and #poll. 🙈

Talking of these, I'd say the "Before epoll" paragraph is, at least partially, wrong. It just omits select/poll. Both are specified in #POSIX (and therefore available on *many* systems), and both offer the same async model, with the drawback of having scalability limitations. As a rule of thumb, they're fine for a few hundred concurrent clients, but not more.

The really wasteful "forking model" (which is kind of classic Unix, really forking one process per client) predates both.

It's really a shame there is no common standard for the modern, really scalable APIs. 😞 We have #epoll, #kqueue, there's "IO completion ports" in Windows, etc. I tend to still use classic #select a lot, if more than a few hundred concurrent (!) clients is nothing you could ever expect for your software, it's still fine.

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