malloc: Trim unused arenas on thread exit

[Florian Weimer]

On 11/14/2017 08:12 AM, Siddhesh Poyarekar wrote:
> On Tuesday 14 November 2017 12:38 PM, Florian Weimer wrote:
>> The trimming really should be a win because the workload is likely to
>> change when a thread exits.
> 
> Not really, worker threads will often have similar workload
> characteristics, e.g. web servers, middleware messaging servers.

But in these cases, the application will generally use a thread pool, so 
glibc will not see the thread exit anyway.

Florian