On 01/21/2014 10:56 AM, Mel Gorman wrote: > On Mon, Jan 20, 2014 at 02:21:06PM -0500, riel@xxxxxxxxxx wrote: >> @@ -1434,6 +1436,11 @@ static void task_numa_placement(struct task_struct *p) >> p->numa_scan_seq = seq; >> p->numa_scan_period_max = task_scan_max(p); >> >> + total_faults = p->numa_faults_locality[0] + >> + p->numa_faults_locality[1] + 1; > > Depending on how you reacted to the review of other patches this may or > may not have a helper now. This is a faults "buffer", zeroed quickly after we take these faults, so we should probably not tempt others by having a helper function to get these numbers... >> + runtime = p->se.avg.runnable_avg_sum; >> + period = p->se.avg.runnable_avg_period; >> + > > Ok, IIRC these stats are based a decaying average based on recent > history so heavy activity followed by long periods of idle will not skew > the stats. Turns out that using a longer time statistic results in a 1% performance gain, so expect this code to change again in the next version :) >> @@ -1458,8 +1465,18 @@ static void task_numa_placement(struct task_struct *p) >> fault_types[priv] += p->numa_faults_buffer[i]; >> p->numa_faults_buffer[i] = 0; >> >> + /* >> + * Normalize the faults_from, so all tasks in a group >> + * count according to CPU use, instead of by the raw >> + * number of faults. Tasks with little runtime have >> + * little over-all impact on throughput, and thus their >> + * faults are less important. >> + */ >> + f_weight = (16384 * runtime * >> + p->numa_faults_from_buffer[i]) / >> + (total_faults * period + 1); > > Why 16384? It looks like a scaling factor to deal with integer approximations > but I'm not 100% sure and I do not see how you arrived at that value. Indeed, it is simply a fixed point math scaling factor. I used 1024 before, but that is kind of a small number when we could be dealing with a node that has 20% of the accesses, and a task that used 10% CPU time. Having the numbers a little larger could help, and certainly should not hurt, as long as we keep the number small enough to avoid overflows. >> p->numa_faults_from[i] >>= 1; >> - p->numa_faults_from[i] += p->numa_faults_from_buffer[i]; >> + p->numa_faults_from[i] += f_weight; >> p->numa_faults_from_buffer[i] = 0; >> > > numa_faults_from needs a big comment that it's no longer about the > number of faults in it. It's the sum of faults measured by the group > weighted by the CPU Agreed. -- All rights reversed -- 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>