Messages in this thread | | | Date | Wed, 6 Jun 2018 06:47:09 -0700 | From | Srikar Dronamraju <> | Subject | Re: [PATCH 18/19] sched/numa: Reset scan rate whenever task moves across nodes |
| |
* Mel Gorman <mgorman@techsingularity.net> [2018-06-05 10:58:43]:
> On Mon, Jun 04, 2018 at 03:30:27PM +0530, Srikar Dronamraju wrote: > > Currently task scan rate is reset when numa balancer migrates the task > > to a different node. If numa balancer initiates a swap, reset is only > > applicable to the task that initiates the swap. Similarly no scan rate > > reset is done if the task is migrated across nodes by traditional load > > balancer. > > > > Instead move the scan reset to the migrate_task_rq. This ensures the > > task moved out of its preferred node, either gets back to its preferred > > node quickly or finds a new preferred node. Doing so, would be fair to > > all tasks migrating across nodes. > > > > By and large you need to be very careful resetting the scan rate without > a lot of justification and I don't think this is enough. With scan rate > resets, there is a significant risk that system CPU overhead is > increased to do the page table updates and handle the resulting minor > faults. There are cases where tasks can get pulled cross-node very > frequently and we do not want NUMA balancing scanning agressively when > that happens. >
I agree with your thoughts here. I will try to see if there are other workloads that benefit from this change. My rational for this change being, because a workload consolidated and slowed down its scanning shouldn't adversely affect it from coming back to its preferred node.
> -- > Mel Gorman > SUSE Labs >
| |