Hi! > The ondemand cpufreq governor uses CPU busy time (e.g. not-idle time) as > a measure for scaling the CPU frequency up or down. > If the CPU is busy, the CPU frequency scales up, if it's idle, the CPU > frequency scales down. Effectively, it uses the CPU busy time as proxy > variable for the more nebulous "how critical is performance right now" > question. > > This algorithm falls flat on its face in the light of workloads where > you're alternatingly disk and CPU bound, such as the ever popular > "git grep", but also things like startup of programs and maildir using > email clients... much to the chagarin of Andrew Morton. > > This patch changes the ondemand algorithm to count iowait time as busy, > not idle, time. As shown in the breakdown cases above, iowait is performance > critical often, and by counting iowait, the proxy variable becomes a more > accurate representation of the "how critical is performance" > question. Well, and now, if you do something like cat /dev/<your usb1.1 hdd> > /dev/null, you'll keep cpu on max frequency. Not a problem for new core i7, but probably big deal for athlon 64. Maybe modern cpus can and should simply react faster? -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
