My Zend.ini:

-showlocation
-showsplash
--launcher.XXMaxPermSize
256m
-startup
plugins/org.zend.php.startup_1.0.0.jar
-vm
/usr/lib/jvm/jre1.6.0_11/lib/i386/client/libjvm.so
-vmargs
-Dorg.eclipse.swt.browser.XULRunnerPath=/usr/local/Zend/ZendStudioForEclipse-6.0.1/plugins/org.mozilla.xulrunner.gtk.linux.x86_1.8.1.3-20070404/xulrunner
#-Dorg.exlipce.swt.browser.XULRunnerPath=/usr/local/Zend/xulrunner/xulrunner
-Xms256M
-Xmx640M
-Xss2m
-XX:PermSize=256m
-XX:MaxPermSize=256m
-XX:ReservedCodeCacheSize=128m
-XX:NewSize=128m
-XX:MaxNewSize=512m
-XX:NewRatio=5
-Xcheck:jni=false
-XX:+RelaxAccessControlCheck

###good###
-XX:+ParallelRefProcEnabled
-XX:+UseBiasedLocking
-XX:+StringCache
-XX:+UseFastAccessorMethods
-XX:+UseFastEmptyMethods
-XX:+UseNiagaraInstrs
-XX:+UseAutoGCSelectPolicy
-XX:+AggressiveOpts
-XX:+BindGCTaskThreadsToCPUs
-XX:+UseGCTaskAffinity
-XX:+UseParallelGC
-XX:LargePageSizeInBytes=64m
-XX:TargetSurvivorRatio=80
-XX:MaxTenuringThreshold=60
-XX:ParallelGCThreads:16
-XX:ParallelCMSThreads:16
-XX:MaxGCPauseMillis=2000
-XX:ThreadStackSize=256
-XX:+UseMPSS
-Xconcurrentio
-XX:+DisableExplicitGC
-XX:+AggressiveHeap
-XX:+AdaptiveSizePolicy

-Dsun.awt.keepWorkingSetOnMinimize=true
-Dsun.java2d.noddraw=true
-Dgnu.gcj.runtime.VMClassLoader.library_control=never
-server

-Xverify:none
-XX:SurvivorRatio=6
-Dosgi.bundlefile.limit=200

###jrockit###
#-XgcPrio:deterministic
#-XgcPrio:pausetime
#-XpauseTarget:250
#-XXcompactratio:1

###good###
-XX:MaxGCPauseMillis=10
-XX:MaxHeapFreeRatio=70

###notgood###
#-XX:+CMSIncrementalMode
#-XX:+CMSIncrementalPacing

-XX:CompileThreshold=1500