Yes this sounds not right… So what are the steps to reproduce ? Fire up a vm, checkout vert.x master and run the build ?
> On 22 Jul 2016, at 00:51, Julien Viet <[email protected]> wrote: > > Hi, > > we are seing OOM "GC overhead limit exceeded" issue in Vert.x test suite on > slow machines like Cloudbees or using virtualization on a laptop. > > This issue means that the VM spend more time in GC than the rest of the VM > (98%), but I’m pretty sure everyone here knows that already. > > In the case of Vert.x testsuite, it happens because we create and destroy > many Vertx instances and therefore many event loops / threads during the > tests. > > I spent quite some time on the issue and I found that it happens because the > ThreadDeatchWatcher's Recycler DELAYED_RECYCLE fast thread local is a > WeakHashMap<Stack, WeakOrderQueue) used by the ThreadPoolCache grows and > retains many entries (up to 2000). This WeakHashMap contains recycled objects > with large footprint and also the Stack itself reference its Thread that has > a large footprint. > > I am not saying it is a leak per se, but the maps grows and takes time to be > garbaged. This does not prevent the testsuite to run on a laptop but it slows > it down and on a slow machines it prevents running the testsuite entirely. > > I believe this behavior was introduced by this commit : > https://github.com/netty/netty/commit/afafadd3d7caf1e4b346da049baab0afeae0a4bc > > The change that makes the whole difference is : > https://github.com/netty/netty/commit/afafadd3d7caf1e4b346da049baab0afeae0a4bc#diff-23eafd00fcd66829f8cce343b26c236aR226 > > The introduction of the field stack in the WeakOrderQueue keeps a reference > on the Stack objects, however Stack instances are also weak keys of the fast > thread local WeakHashMap and therefore defeats the purpose of the > WeakHashMap. Not entirely as it is GC’ed but much less often and increase the > memory footprint. > > let me know what you think > > Julien > > -- > You received this message because you are subscribed to the Google Groups > "Netty discussions" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/netty/2A547499-D279-4286-AA95-3447EE2B621E%40julienviet.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Netty discussions" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/netty/D5C167E1-D3C3-4B8F-B4B8-FD4D1793BC1F%40googlemail.com. For more options, visit https://groups.google.com/d/optout.
