* Randy Dunlap ([EMAIL PROTECTED]) wrote: [fixing the rest of the comments in the patch] > What character is this that I cannot read (not displayed properly > by my email client maybe)? <something> after 644.09 and before the > +- symbol, repeated just before all of the +- symbols. >
This file seems to be UTF-8 and the mail has been send by quilt. Is it ok or should I change this to +/- just to make sure ? > > > +Getppid without memory pressure: > > +1462.09±18.87 - 150.92±1.01 = 1311.17±18.90 cycles > > + > > +Getppid with memory pressure: > > +17113.33±1655.92 - 578.22±269.51 = 16535.11±1677.71 cycles > > + > > +Therefore, if we add 2 markers not based on immediate values to the getppid > > +code, which would add 2 memory reads, we would add > > +2 * 555.93±12.74 = 1111.86±25.48 cycles > > + > > +Therefore, > > + > > +1111.86±25.48 / 16535.11±1677.71 = 0.0672 > > + relative error: sqrt(((25.48/1111.86)^2)+((1677.71/16535.11)^2)) > > + = 0.1040 > > + absolute error: 0.1040 * 0.0672 = 0.0070 > > + > > +Therefore: 0.0672±0.0070 * 100% = 6.72±0.70 % > > + > > +We can therefore affirm that adding 2 markers to getppid, on a system with > > high > > +memory pressure, would have a performance hit of at least 6.0% on the > > system > > +call time, all within the uncertainty limits of these tests. The same > > applies to > > +other kernel code paths. The smaller those code paths are, the highest the > > +impact ratio will be. > > + > > +Therefore, not only is it interesting to use the immediate values to > > dynamically > > +activate dormant code such as the markers, but I think it should also be > > +considered as a replacement for many of the "read mostly" static variables. > > > --- > ~Randy > *** Remember to use Documentation/SubmitChecklist when testing your code *** > -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
