Sorry the list address was not correct On Mon, 24 Nov 2014, Christoph Lameter wrote: > Recently a lot of work has been done in the kernel to be able to keep OS > threads off low latency cores with the NOHZ work mainly pushed by Frederic > Weisbecker (also also Paul McKenney modifying RCU for that purpose). With > that approach we may now reduce the timer tick to a frequency of 1 per > second. The result of that work is now available in Redhat 7. > > I have recently submitted work on the vmstat kworkers that makes the > kworkers run on demand with a shepherd worker checking from a non low > latency processor if there is actual work to be done on a processor in low > latency mode. If not then the kworker requests can be avoided and > therefore activities on that processor are reduced. This approach can be > extended to cover other necessary activities on low latency cores. > > There is other work in progress to limit unbound kworker threads to no > NOHZ processors. Also more work is in flight to work on various issues in > the scheduler to enable us to hold off the timer tick for more than one > second. > > There are numerous other issues that can impact on a low latency core from > the memory management system. I would like to discuss ways that we can > further ensure that OS activities do not impact latency critical threads > running on special nohz cores. > > This may cover: > - minor and major faults and how to suppress them effectively. > - Processor cache impacts by sibling threads. > - IPIs > - Control over various subsystem specific per cpu threads. > - Control impacts of scans for defragmentation and THP on these cores. > > There was a recent discussion on the subject matter on lkml that mentions > a number of the pending issues in this area: > > https://lkml.org/lkml/2014/11/11/679 > https://lkml.org/lkml/2014/10/31/364 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>