If there is unnecessary casting or boxing, how do you avoid it? hinting and casting affect it, but not in ways I understand, or can predict.
On Wednesday, January 30, 2019 at 6:06:37 PM UTC-8, Alex Miller wrote: > > Sometimes the insertion of profiling instrumentation magnifies the cost of > things in a hot loop or provides misleading hot spot info. If you're using > a tracing profiler, you might try sampling instead as it's less prone to > this. > > Or, this sounds silly, but you can manually sample by just doing a few > thread dumps while it's running (either ctrl-\ or externally with kill -3) > and see what's at the top. If there really is a hot spot, this is a > surprisingly effective way to see it. > > For this kind of code, there is no substitute for actually reading the > bytecode and thinking carefully about where there is unnecessary casting or > boxing. > > > > On Wed, Jan 30, 2019 at 6:55 PM Brian Craft <craft...@gmail.com > <javascript:>> wrote: > >> I haven't tried much. I'm getting the java via clj-java-decompiler.core >> 'decompile' macro. >> >> A long cast does drop the cast (which is really counter-intuitive: >> explicitly invoke 'long', which calls longCast, in order to avoid calling >> longCast). >> >> Amusingly this doesn't reduce the total run-time, though longCast drops >> out of the hotspot list. :-p There must be some other limiting step that >> I'm missing in the profiler. >> >> I'm calling it around 1.2M times, so hopefully that engages the jit. >> >> On Wednesday, January 30, 2019 at 3:39:41 PM UTC-8, Alex Miller wrote: >>> >>> What have you tried? And how are you getting that Java? I would prefer >>> to look at bytecode (via javap) to verify what you're saying. >>> >>> Have you tried an explicit long cast? >>> >>> (aget flat-dict (bit-and 0xff (long (aget arr j)))) >>> >>> Are you running this hot enough for the JIT to kick in? Usually this is >>> the kind of thing it's good at, but it might take 10k invocations before it >>> does. >>> >>> >>> On Wednesday, January 30, 2019 at 4:03:43 PM UTC-6, Brian Craft wrote: >>>> >>>> Profiling is showing a lot of time spent in RT.longCast, in places like >>>> this: >>>> >>>> (aget flat-dict (bit-and 0xff (aget arr j))) >>>> >>>> arr is hinted as ^bytes, and flat-dict as ^objects. >>>> >>>> which compiles to this: >>>> >>>> Object code2 = RT.aget((Object[])flat_dict, RT.intCast(0xFFL & >>>> RT.longCast((Object)RT.aget((byte[])arr2, RT.intCast(k))))) >>>> >>>> Is there any way to avoid that RT.longCast? There is an aget method in >>>> RT.java that returns a byte, and a longCast for byte, but I suspect the >>>> cast to Object is causing it to hit the longCast for Object, which does a >>>> bunch of reflection. >>>> >>> -- >> You received this message because you are subscribed to the Google >> Groups "Clojure" group. >> To post to this group, send email to clo...@googlegroups.com >> <javascript:> >> Note that posts from new members are moderated - please be patient with >> your first post. >> To unsubscribe from this group, send email to >> clojure+u...@googlegroups.com <javascript:> >> For more options, visit this group at >> http://groups.google.com/group/clojure?hl=en >> --- >> You received this message because you are subscribed to a topic in the >> Google Groups "Clojure" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/clojure/vXJFuOujTaw/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> clojure+u...@googlegroups.com <javascript:>. >> For more options, visit https://groups.google.com/d/optout. >> > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
