>>>>> "Hidetoshi" == Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx> writes: >> [9/9] ia64_acct_get_vtime.patch Hidetoshi> Now all check points are ready. Hidetoshi> We already cumulate cycles for stime/utime on kernel Hidetoshi> entrance/exit, so what we need to do is reflecting them Hidetoshi> into stime/utime of the thread, after translating cycles to Hidetoshi> nsec. This patchset duplicates some of the Microstate Accounting patchset (which attempts to keep track of time spent in various states for each thread). As such I've had some experience trying to do this stuff. Things to watch are: -- With Montvale and later, the processor clock speed can be varied via ACPI. Does ITC rate change? In additon, KVM can virtualise ITC (although it doesn't at present) -- ITC is not synchronised across multiple processors. I don't think this'll be an issue for you as you're only measuring time on-cpu, and migration necessarily goes via a run queue. -- Adding ACCOUNT_SYS_ENTER adds around 40 cycles to the system call path. If you wanted, you could move reading ITC earlier (it takes up to 36 cycles), and overlap with other work. Peter C -- Dr Peter Chubb http://www.gelato.unsw.edu.au peterc AT gelato.unsw.edu.au http://www.ertos.nicta.com.au ERTOS within National ICT Australia - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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