1 =================
2 Scheduler debugfs
3 =================
4
5 Booting a kernel with CONFIG_SCHED_DEBUG=y wil
6 scheduler specific debug files under /sys/kern
7 those files are described below.
8
9 numa_balancing
10 ==============
11
12 `numa_balancing` directory is used to hold fil
13 balancing feature. If the system overhead fro
14 high then the rate the kernel samples for NUMA
15 controlled by the `scan_period_min_ms, scan_de
16 scan_period_max_ms, scan_size_mb` files.
17
18
19 scan_period_min_ms, scan_delay_ms, scan_period
20 ----------------------------------------------
21
22 Automatic NUMA balancing scans tasks address s
23 detect if pages are properly placed or if the
24 memory node local to where the task is running
25 scans the next "scan size" number of pages in
26 end of the address space is reached the scanne
27
28 In combination, the "scan delay" and "scan siz
29 When "scan delay" decreases, the scan rate inc
30 hence the scan rate of every task is adaptive
31 behaviour. If pages are properly placed then t
32 otherwise the scan delay decreases. The "scan
33 the higher the "scan size", the higher the sca
34
35 Higher scan rates incur higher system overhead
36 trapped and potentially data must be migrated.
37 rate, the more quickly a tasks memory is migra
38 workload pattern changes and minimises perform
39 memory accesses. These files control the thres
40 the number of pages scanned.
41
42 ``scan_period_min_ms`` is the minimum time in
43 tasks virtual memory. It effectively controls
44 rate for each task.
45
46 ``scan_delay_ms`` is the starting "scan delay"
47 initially forks.
48
49 ``scan_period_max_ms`` is the maximum time in
50 tasks virtual memory. It effectively controls
51 rate for each task.
52
53 ``scan_size_mb`` is how many megabytes worth o
54 a given scan.
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