> > > > > > refresh_zone_stat_thresholds function has two loops which is > > > expensive for higher number of CPUs and NUMA nodes. > > > > > > Below is the rough estimation of total iterations done by these > > > loops based on number of NUMA and CPUs. > > > > > > Total number of iterations: nCPU * 2 * Numa * mCPU > > > Where: > > > nCPU = total number of CPUs > > > Numa = total number of NUMA nodes > > > mCPU = mean value of total CPUs (e.g., 512 for 1024 total CPUs) > > > > > > For the system under test with 16 NUMA nodes and 1024 CPUs, this > > > results in a substantial increase in the number of loop iterations > > > during boot-up when NUMA is enabled: > > > > > > No NUMA = 1024*2*1*512 = 1,048,576 : Here > > refresh_zone_stat_thresholds > > > takes around 224 ms total for all the CPUs in the system under test. > > > 16 NUMA = 1024*2*16*512 = 16,777,216 : Here > > > refresh_zone_stat_thresholds takes around 4.5 seconds total for all > > > the CPUs in the system under test. > > > > > > Calling this for each CPU is expensive when there are large number > > > of CPUs along with multiple NUMAs. Fix this by deferring > > > refresh_zone_stat_thresholds to be called later at once when all the > > > secondary CPUs are up. Also, register the DYN hooks to keep the > > > existing hotplug functionality intact. > > > > > > Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx> > > > > CC: Mel Gorman and Christoph Lameter > > > Adding cl@xxxxxxxxx instead of clameter@xxxxxxx for Christoph Lameter > > - Saurabh Hi Andrew, Can we get this merge in for next kernel release. Please let me know if there is any concern with this patch. Regards, Saurabh
