On Sat, 2004-11-13 at 18:35 +0100, Arjan van de Ven wrote: > On Sat, 2004-11-13 at 12:18 -0500, Owen Taylor wrote: > > Ideally, system boot would involve a 3-4 second sequential read of > > around 100 megabytes of data from the hard disk, > > make that 7 seconds.. > Note: I did this experiment about a year ago, during boot first read > everything into cache and then do the rest of boot basically without > disk IO (there are some writes but that's async). > The total time to boot did not decrease ...... That experiment was one of the things that convinced me that getting a good visualization of the critical path is crucial to actually speeding up the boot process. > > CPU utilization would > > be parallelized with that, and all queries on external systems would > > be asynchronous ... startup continues and once the external system > > responds, the system state is updated. Plausibly the user could start > > work under 10 seconds on this ideal system. > > given the 7 second disk read time... 10 seconds is a bit unrealistic. > One of the critical paths will be getting an IP address and mounting the > /home dir over nfs... ethernet negotiation can easily be 10 seconds > already with gige, and DHCP is depending on that to complete before it > can get a lease. I'd agree 10 seconds isn't a realistic target; my point was more that if we have only 7 seconds of disk access, and, say, 10 seconds of computation to do, and maybe 15 seconds too negotiate gige, get a dhcp lease, and mount your homedir (if relevant), then the time between 15 seconds and 2 minutes needs to be investigated in terms of dependencies. > One of the things we should investigate is just reduce the shere number > of different files that get opened.... its about 11000 iirc right now. If we're actually spending all our time waiting on a DHCP lease, or for probing serial mice to timeout, then 11000 opens don't matter a whole lot. Not that eliminating the opens isn't a good idea... Regards, Owen
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