<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Nov 22, 2017, at 7:49 PM, Pete Heist <<a href="mailto:peteheist@gmail.com" class="">peteheist@gmail.com</a>> wrote:</div><div class=""><div class=""><br class=""><blockquote type="cite" class="">On Nov 22, 2017, at 7:38 PM, Dave Taht <<a href="mailto:dave.taht@gmail.com" class="">dave.taht@gmail.com</a>> wrote:<br class=""><br class="">It is somewhat unfair to not include the pfifo bandwidth on the test<br class="">(a cpu cost/byte might be a better metric), also pfifo_fast has three<br class="">tiers of classification in it.<br class=""></blockquote><br class="">Yeah, it’s probably better to not try to subtract the pfifo_fast system time out in the way that I did. I should probably just compare cake with and without the change, using a more accurate tool.<br class=""><br class="">I don’t see how the change could hurt, but I also now am not sure it helps much either. I guess it’s just two divs per call to cake_hash, which is obviously going to happen more at GigE.<br class=""></div></div></blockquote></div><div class=""><br class=""></div><div class="">I didn’t figure out ‘perf’ for this, but I did instrument cake_hash in a simple way with calls to local_clock_ns using ‘stap'. Results on stap tab:</div><div class=""><br class=""></div><div class=""><a href="https://docs.google.com/spreadsheets/d/1LKoq5NaswuHm9H1atXoZA1AhNDg6L4UYS3Pn5lCsb1I/edit#gid=1493356365" class="">https://docs.google.com/spreadsheets/d/1LKoq5NaswuHm9H1atXoZA1AhNDg6L4UYS3Pn5lCsb1I/edit#gid=1493356365</a></div><div class=""><br class=""></div><div class="">It’s a head scratcher, but I saw about a 3% mean time reduction in cake_hash for the “optimized” version when limited at 950mbit, and a very slight slowdown when unlimited. “Confounding”...(by Estee Lauder).</div><div class=""><br class=""></div><div class="">Whether or not those results are either correct or statistically significant, it doesn’t look like it’s worth too much more effort, and I can leave it to you whether you want this change or not. I don’t see the harm in it, and neither do I see much of a benefit.</div></body></html>