On 1/21/19 7:49 PM, Ondřej Kuzník wrote: Duuh, right. I got stuck looking for what's special about the indexing task and couldn't find it:-( I need to make it special. So, let tasks declare their expected speed until finish or between pausechecks. At FAST=1 (default) and SLOW=0. A pause only stops tasks with speed < ltp_pause. In thread_pool_pause(), replace the WANT_PAUSE stage with while (++ltp_pause <= max speed) { wait until no more tasks with speed < ltp_pause; } Then fast tasks should breeze past slow ones when preparing to pause. Until all threads have slow tasks, anyway. To mitigate that, we'd need to predeclare the speed when submitting a task, and limit the number of parallel slow tasks. pool_submit() could stash the rest in a "slow queue" instead of submitting. But I don't want to go there yet.