Of course, you'll hit the nightmarish "CMS fragement" easier if NewSize too low:) Generally speaking, most of YGC should be less than 5ms for a normal size heap. maybe your load is too high or there're vm options be misconfigured ? ________________________________________ 发件人: Varun Sharma [[email protected]] 发送时间: 2013年2月21日 15:32 收件人: [email protected] 主题: GC frequency
Hi, I have a system tuned with new Gen 512M with a lot write load. The system has 4 cores - ParNewGC and GCThreads is set to 4. I am using ConcMarkGC and CMSInitiating fraction is set to 60 %. I am observing the 90th/99th percentile of latency and see it highly correlated with GC pauses. There are times when I have a GC pause of ~ 200 ms every 4 seconds - the tail latency shoots up to 200 milliseconds for reads - most reads are being served out of cache. Looking at the GC log and tail latency pattern, there is direct correlation b/w the two. When the write load is low, and the GC pauses are like 100-150 ms every 6 seconds, the tail latency improves. After seeing this behaviour, I am intent on reducing the NewSize to 256M but I risk 100 ms pauses pretty much every 1-2 seconds and perhaps higher chance of promotion failures (MSLAB etc. is on). Does anyone know if frequent young gen collections can be a problem ? Thanks Varun
