On Wed, Jul 14, 2021 at 10:57 AM Jeff King <peff@xxxxxxxx> wrote: > > On Wed, Jul 14, 2021 at 10:32:56AM -0700, Elijah Newren wrote: > > > > It's slightly sad that we only got a 30% CPU improvement in the past 10 > > > years. Are you just counting clock speed as a short-hand here? I think > > > that doesn't tell the whole story. But all of this is a side-note > > > anyway. What I care about is your actual timings. :) > > > > I'm using shorthand when discussing file sizes above (though I used > > actual measurements when picking new values below). But the 30% came > > from measuring the timings with the exact same sample file as you and > > using a lightly modified version of your original script (tweaked to > > also change file basenames) on an AWS c5xlarge instance. My timings > > showed they were only about 30% faster than what you got when you last > > bumped the limits. > > Interesting. My timings are much faster. With a 20k file, I get (on my > laptop, which is an i9-9880H): > > N CPU (2008) CPU (now) > 10 0.43s 0.007s > 100 0.44s 0.071s > 200 1.40s 0.226s > 400 4.87s 0.788s > 800 18.08s 2.887s > 1000 27.82s 4.431s > > The 2008 timings are from the old email you linked in your commit > message, and the new one is from running the revised script you showed. > The savings seem like more than 30%. I don't know if that's all CPU or > if something changed in the code. I was using the script you wrote in 2008, but comparing to your reported numbers in 2011[1]. When you bumped in 2011, you said you picked the limits of 400 & 1000 in order to give rough timings of 2s and 10s. So the table looks more like: N CPU (2008) CPU (2011) c5xlarge CPU (yours) 400 4.87s ~2s 1.106s 0.788s 1000 27.82s ~10s 6.350s 4.431s So, 2011->c5xlarge on these (just recomputed now numbers) show improvements of ~45% and ~36%. Maybe I had an outlier run earlier that was in the upper 6s range for N=1000 and I rounded off to 30% for the commit message? Don't know, those numbers are on a laptop that died in the last few days. But yeah, you are seeing a bigger improvement than I did; 2011->your current laptop shows roughly 56% - 60% improvement. [1] https://lore.kernel.org/git/20110219102128.GB22508@xxxxxxxxxxxxxxxxxxxxx/ > Using a 3k file (the median for ls-tree), numbers are similar, but a > little smaller (my n=1300 is about 1.4s). So I think we're both in the > same ballpark (and certainly an AWS machine is a perfectly fine > representative sample of where people might run Git). Yeah, dividing any of the timings I get by the ones you get seem to be giving a value somewhere around 1.4, so that seems reassuring on the consistency front. That doesn't fix my jealousy of your faster CPU, but that's a separate problem. :-)
