Re: Using ProcSignal to get memory context stats from a runningbackend

Hi,

On 2017-12-21 15:13:13 +0800, Craig Ringer wrote:
> There tons of callers to  enlargeStringInfo, so a 'noerror' parameter would
> be viable.

Not sure what you mean with that sentence?


> But I'm not convinced it's worth it personally. If we OOM in response to a
> ProcSignal request for memory context output, we're having pretty bad luck.
> The output is 8k in my test. But even if it were a couple of hundred kb,
> happening to hit OOM just then isn't great luck on modern systems with many
> gigabytes of RAM.

I've seen plenty memory dumps in the dozens to hundreds of
megabytes. And imo such cases are more likely to invite use of this
facility.


> If that *does* happen, repalloc(...) will call
> MemoryContextStats(TopMemoryContext) before returning NULL. So we'll get
> our memory context dump anyway, albeit to stderr.

That would still abort the query that might otherwise continue to work,
so that seems no excuse.

Greetings,

Andres Freund