On Wed, Jan 15, 2020 at 02:42:51PM -0800, Paul E. McKenney wrote: > > [snip] > > > > We can certainly refine it further but at this time I am thinking of spending > > > > my time reviewing Lai's patches and learning some other RCU things I need to > > > > catch up on. If you hate this patch too much, we can also defer this patch > > > > review for a bit and I can carry it in my tree for now as it is only a patch > > > > to test code. But honestly, in its current form I am sort of happy with it. > > > > > > OK, I will keep it as is for now and let's look again later on. It is not > > > in the bucket for the upcoming merge window in any case, so we do have > > > quite a bit of time. > > > > > > It is not that I hate it, but rather that I want to be able to give > > > good answers to questions that might come up. And given that I have > > > occasionally given certain people a hard time about their statistics, > > > it is only reasonable to expect them to return the favor. I wouldn't > > > want you to be caught in the crossfire. ;-) > > > > Since the weights were concerning, I was thinking of just using a weight of > > (1 / N) where N is the number of samples. Essentially taking the average. > > That could be simple enough and does not cause your concerns with weight > > tuning. I tested it and looks good, I'll post it shortly. > > YES!!! ;-) > > Snapshot mem_begin before entering the loop. For the mean value to > be solid, you need at least 20-30 samples, which might mean upping the > default for kfree_loops. Have an "unsigned long long" to accumulate the > sum, which should avoid any possibility of overflow for current systems > and for all systems for kfree_loops less than PAGE_SIZE. At which point, > forget the "%" stuff and just sum up the si_mem_available() on each pass > through the loop. > > Do the division on exit from the loop, preferably checking for divide > by zero. > > Straightforward, fast, reasonably reliable, and easy to defend. I mostly did it along these lines. Hopefully the latest posting is reasonable enough ;-) I sent it twice because I messed up the authorship (sorry). thanks, - Joel
