All, A longstanding problem that we have had is that enablings on defunct providers (e.g., USDT probes on dead processes) are not reaped: the probes will exist as long as there exists an enabling for them. When processes are turning over frequently (or when enablings are long-running), this can clog up the probe space to the point that DTrace probe creation will silently fail (an absolutely maddening failure mode). This has been hit several times over the years (we were nailed by it on our build machines at Fishworks) -- so when Theo Schlossnagle mentioned to me that he was getting killed by this problem in an environment with rapidly turning over Postgres processes, I was embarrassed that I hadn't tackled it earlier. As it turns out, it was a tad thorny for locking reasons, but a patch for this problem is attached. We have integrated this into our bits at Joyent (internal ticket is OS-454, "enablings on defunct providers prevent providers from unregistering"), so you'll see this show up soon at http://github.com/joyent/illumos-joyent -- but I wanted to give everyone here a heads-up.
Anyway, patch is attached, with my thanks to Adam for a helpful
discussion on fasttrap's asynchronous provider retiring mechanics.
Note that Adam hasn't (yet) reviewed this, and its integration
upstream should wait until he's had a chance to look it over. Please
let me know if you have any questions or comments!
Thanks,
Bryan
dtrace-reap.patch
Description: Binary data
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