On Mon, Mar 06, 2017 at 02:42:25PM -0500, Tejun Heo wrote: >Hello, Wei. > >On Fri, Feb 17, 2017 at 10:12:31PM +0800, Wei Yang wrote: >> > And compare the ruling with the iteration for the loop to be (1UL << >> > 5) and (1UL << 19). >> > The runtime is 0.00s and 0.04s respectively. The absolute value is not much. > >systemd-analyze usually does a pretty good job of breaking down which >phase took how long. It might be worthwhile to test whether the >improvement is actually visible during the boot. > Hi, Tejun Thanks for your suggestion. I have tried systemd-analyze to measure the effect, while looks not good. Result without patch ------------------------- Startup finished in 7.243s (kernel) + 25.034s (userspace) = 32.277s Startup finished in 7.254s (kernel) + 19.816s (userspace) = 27.071s Startup finished in 7.272s (kernel) + 4.363s (userspace) = 11.636s Startup finished in 7.258s (kernel) + 24.319s (userspace) = 31.577s Startup finished in 7.262s (kernel) + 9.481s (userspace) = 16.743s Startup finished in 7.266s (kernel) + 14.766s (userspace) = 22.032s Avg = 7.259s Result with patch ------------------------- Startup finished in 7.262s (kernel) + 14.294s (userspace) = 21.557s Startup finished in 7.264s (kernel) + 19.519s (userspace) = 26.783s Startup finished in 7.266s (kernel) + 4.730s (userspace) = 11.997s Startup finished in 7.258s (kernel) + 9.514s (userspace) = 16.773s Startup finished in 7.258s (kernel) + 14.371s (userspace) = 21.629s Startup finished in 7.258s (kernel) + 14.627s (userspace) = 21.885s Avg = 7.261s It looks the effect is not obvious. Maybe the improvement is not good enough :( >> >> * Do we really need to add full reverse iterator to just get the >> >> highest section number? >> >> >> > >> > You are right. After I sent out the mail, I realized just highest pfn >> > is necessary. > >That said, getting efficient is always great as long as the added >complexity is justifiably small enough. If you can make the change >simple enough, it'd be a lot easier to merge. > Agree. I have replaced the reverse iteration with a simple last pfn return. The test result above is based on the new version. >Thanks. > >-- >tejun -- Wei Yang Help you, Help me
Attachment:
signature.asc
Description: PGP signature
