Tuning-advise for soft-realtime systems

[Jason Evans]

On Mar 14, 2016, at 10:52 AM, Clemens Eisserer <linuxhippy at gmail.com> wrote:
> I am currently evaluating jemalloc for a soft-realtime system where
> worst-case latency is of concern.
> When allocating areas of random size honoring the size-distribution
> which is to be expected, usually latency is of no concern.
> However, from time to time there are latency spikes of ~300
> microseconds for a single malloc especially for mid-sized allocations
> (e.g. 1024byte).
> 
> My guess is those latency spikes arise when jemalloc requests
> additional memory for it's arena's from the kernel.
> Are there any tuning knobs to reduce the duration of those spikes and
> instead increasing there frequency?

The top suggestions I can think of are to disable unused dirty page purging, and to increase the chunk size to the largest size you can tolerate in terms of memory usage.

Jason