On Fri, May 16, 2008 at 1:41 PM, Aleksey Shipilev <[EMAIL PROTECTED]> wrote: > Aha, so it's literally no way to disable buffered hashcode? That means > identityHashCode GC helper can't be implemented as magic.
Why not? GC helper doesn't need to include buffered hash. Thanks, xiaofeng > That's too bad, my profiling and measurements shows that > identityHashCode computation is really hot on serialization workload > and I'm pretty sure the same picture shows up on any IdentityHashMap > user. Simple substitution of GC call in > VMMemoryManager.getIdentityHashCode with ((jint)jobj->object >> 2) > gives +20% boost to serialization benchmark even with JNI overhead in > place. > > Thanks, > Aleksey. > > On Fri, May 16, 2008 at 3:42 AM, Xiao-Feng Li <[EMAIL PROTECTED]> wrote: >> Aleksey, "attached hashcode" works together with "buffered hashcode". >> "Buffered hashcode" is created in compacting GC (in other words, in >> major collection). So if normally there is few major collections, >> there will be very few buffered hashcodes created. In minor >> collections, it uses the attached hashcode. >> >> Thanks, >> xiaofeng >> >> On Fri, May 16, 2008 at 5:06 AM, Aleksey Shipilev >> <[EMAIL PROTECTED]> wrote: >>> Hi, Xiao Feng, GC gurus, >>> >>> I'm back to IdentityHashCode implementation on magics [1]. I had >>> managed to inline the helper for System.identityHashCode(), but >>> unfortunately I had stuck with buffered hashcode scheme. Basically, >>> there is no support for buffered hashcodes in GCHelper and I doubt it >>> could be implemented there as we need to traverse native data >>> structure on hashcode lookup. Not saying about performance when there >>> are many hashcodes in the run, I have a suspicion there is the problem >>> too. >>> >>> So I wonder whether is it possible to turn on "attached hashcode" >>> instead of "buffered hashcode" somehow to see the performance impact? >>> I searched through sources and it's still unclear for me. >>> >>> Thanks, >>> Aleksey. >>> >>> [1] https://issues.apache.org/jira/browse/HARMONY-5713 >>> >> >> >> >> -- >> http://xiao-feng.blogspot.com >> > -- http://xiao-feng.blogspot.com
