* David Holmes: > My thoughts haven't really changed since 2015 - and sadly neither has > there been any change in glibc in that time. Nor, to my recollection, > have there been any other reported issues with this.
The issue gets occasionally reported by people who use small stacks with large initial-exec TLS consumers (such as jemalloc). On the glibc side, we aren't entirely sure what to do about this. We have recently tweaked the stack size computation, so that in many cases, threads now receive an additional page. This was necessary to work around a kernel/hardware change where context switches started to push substantially more data on the stack than before, and minimal stack sizes did not work anymore on x86-64 (leading to ntpd crashing during startup, among other things). The main concern is that for workloads with carefully tuned stack sizes, revamping the stack size computation so that TLS is no longer effectively allocated on the stack might result in address space exhaustion. (This should only be a concern on 32-bit architectures.) Even if we changed this today (or had changed it in 2015), it would take a long time for the change to end up with end users, so it's unclear how much help it would be. Maybe OpenJDK can add a property specifying a stack size reserve, and htis number is added to all stack size requests? This will at least allow users to work around the issue locally. If we change the accounting in glibc, we will have to add a similar tunable on the glibc side, too. Thanks, Florian
