Comments on: Polling is always wrong http://porkrind.org/missives/polling-is-always-wrong/ Portal For The Masses Thu, 26 Jan 2012 00:00:39 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Jeff Connelly http://porkrind.org/missives/polling-is-always-wrong/comment-page-1/#comment-48 Jeff Connelly Wed, 26 Mar 2008 19:06:07 +0000 http://porkrind.org/missives2/?p=21#comment-48 <p>Agree with your general point, but in some situations polling can work better than only using interrupts — for example, FreeBSD has polling support in some network device drivers. From http://info.iet.unipi.it/~luigi/polling/ :<br /> —<br /> “Device polling” (polling for brevity) refers to a technique for handling devices which does not rely on the latter to generate interrupts when they need attention, but rather lets the <span class="caps">CPU</span> poll devices to service their needs. This might seem inefficient and counterintuitive, but when done properly, polling gives more control to the operating system on when and how to handle devices, with a number of advantages in terms of system responsivity and performance, as described below.<br /> —</p> <p>Although, technically this is a mix of polling and interrupting, since the clock interrupt is used to control when polling occurs. Nonetheless, polling actually uses less <span class="caps">CPU</span> under heavy load, primarily because of less overhead (context switches can be eliminated in most cases).</p> Agree with your general point, but in some situations polling can work better than only using interrupts — for example, FreeBSD has polling support in some network device drivers. From http://info.iet.unipi.it/~luigi/polling/ :
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“Device polling” (polling for brevity) refers to a technique for handling devices which does not rely on the latter to generate interrupts when they need attention, but rather lets the CPU poll devices to service their needs. This might seem inefficient and counterintuitive, but when done properly, polling gives more control to the operating system on when and how to handle devices, with a number of advantages in terms of system responsivity and performance, as described below.
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Although, technically this is a mix of polling and interrupting, since the clock interrupt is used to control when polling occurs. Nonetheless, polling actually uses less CPU under heavy load, primarily because of less overhead (context switches can be eliminated in most cases).

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