On Fri, 2007-11-30 at 11:08 +0100, Ingo Molnar wrote: > * Nick Piggin <[EMAIL PROTECTED]> wrote: > > > Haven't we been asking JVMs to use futexes or posix locking for years > > and years now? [...] > > i'm curious, with what JVM was it tested and where's the source so i can > fix their locking for them? Can the problem be reproduced with: > > > http://download.fedora.redhat.com/pub/fedora/linux/development/source/SRPMS/java-1.7.0-icedtea-1.7.0.0-0.20.b23.snapshot.fc9.src.rpm I used BEA Jrockit to run volanoMark. Because of no Jrockit source codes, so I retested volanoMark by jre-1.7.0-icedtea.x86_64 java of Fedora Core 8 on my stoakley (8-core) machine with kernel 2.6.24-rc3.
1) Jrockit: sched_compat_yield=0's result is less than 15% of sched_compat_yield=1's. 2) jre-1.7.0-icedtea: sched_compat_yield=0's result is less than 89% of sched_compat_yield=1's. So JVM really has much impact on the regression. I checked the source codes of openjdk and found Thread.yield is implemented as native sched_yield. If java applications call Thread.yield, it just calls sched_yield. garbage collection and other JVM threads also calls Thread.yield. That's why 2 different JVM have different regression percentage. Although no source codes of volanoMark, I suspect it calls Thread.sched. volanoMark is a kind of chatroom benchmark. When a client sends out a message, server will send the message to all clients. I suspect the client calls Thread.yield after sending out a couple of messages. 2 JVM all have regression if sched_compat_yield=0. I ran some testing, such like iozone/specjbb/tbench/dbench/sysbench, and didn't see regression. -yanmin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
