On Friday 27 April 2007 02:54, James Ketrenos wrote: > Anyway, I ran a quick test of using hw_scan enabled and disabled on a > system with 15 active and 17 passive channels. > > hw scan: 2.2s > sw scan: 4.7s > > So the SW scan wasn't the 10s that I stated before (although it sure felt > like 10s before I ran it with 'time') But anyway... the hw scan is > currently beating out sw scanning by ~54%, at least here. > Ok. Let's try interpreting these numbers. The current settings in mac80211 give each active scan channel 1/33rd of a second to send a probe request and another 1/33rd of a second to listen for any replies. That means, at the very minimum, an active scan will take a bit over 60 ms to complete per channel. For passive scans, each channel gets 1/5th of a second, so that's 200 ms right there. With all this, we get: .06 (s/channel) * 15 channels + .2 (s/channel) * 17 channels = 4.3 s So, 91% of the time that software scan takes is just.. waiting. HW scan simply "wins" by default because it doesn't wait as long. These numbers say nothing about the actual overhead of using SW vs. HW scanning. Can you provide more details on the delays that iwlwifi uses so we can do a proper comparison? -Michael Wu
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