CentOS 8

cpu_num

CPUs

The number of CPUs available in the system (physical and logical)

cpu_util

percent

The average CPU utilization % across all the CPUs (i.e., how much time on average the CPUs are busy doing work)

cpu_util_details

percent

The average CPU utilization % broken down by usage type and cpu number (e.g., cp1 user, cp2 system, cp3 soft-irq)

cpu_load_avg

tasks

The system load average (i.e., the number of active tasks in the system)

mem_util

percent

The memory utilization % (i.e, the % of memory used)

mem_util_nocache

percent

The memory utilization % (i.e., the % of memory used) without considering memory reserved for caching purposes

mem_util_details

percent

The memory utilization % (i.e., the % of memory used) broken down by usage type (e.g., active memory)

mem_used

bytes

The total amount of memory used

mem_used_nocache

bytes

The total amount of memory used without considering memory reserved for caching purposes

mem_total

bytes

The total amount of installed memory

mem_fault_minor

faults/s

The number of minor memory faults (i.e., faults that do not cause disk access) per second

mem_fault_major

faults/s

The number of major memory faults (i.e., faults that cause disk access) per second

mem_fault

faults/s

The number of memory faults (major + minor)

mem_swapins

pages/s

The number of memory pages swapped in per second

mem_swapouts

pages/s

The number of memory pages swapped out per second

network_tcp_retrans

retrans/s

The number of network TCP retransmissions per second

network_in_bytes_details

bytes/s

The number of inbound network packets in bytes per second broken down by network device (e.g., wlp4s0)

network_out_bytes_details

bytes/s

The number of outbound network packets in bytes per second broken down by network device (e.g., eth01)

disk_swap_util

percent

The average space utilization % of swap disks

disk_swap_used

bytes

The total amount of space used by swap disks

disk_util_details

percent

The utilization % of disk, i.e how much time a disk is busy doing work broken down by disk (e.g., disk D://)

disk_iops_writes

ops/s

The average number of IO disk-write operations per second across all disks

disk_iops_reads

ops/s

The average number of IO disk-read operations per second across all disks

disk_iops

ops/s

The average number of IO disk operations per second across all disks

disk_response_time_read

seconds

The average response time of IO read-disk operations

disk_response_time_worst

seconds

The average response time of IO disk operations of the slowest disk

disk_response_time_write

seconds

The average response time of IO write-disk operations

disk_response_time_details

ops/s

The average response time of IO disk operations broken down by disk (e.g., disk /dev/nvme01 )

disk_iops_details

ops/s

The number of IO disk-write operations of per second broken down by disk (e.g., disk /dev/nvme01)

disk_io_inflight_details

ops

The number of IO disk operations in progress (outstanding) broken down by disk (e.g., disk /dev/nvme01)

disk_write_bytes

bytes/s

The number of bytes per second written across all disks

disk_read_bytes

bytes/s

The number of bytes per second read across all disks

disk_read_write_bytes

bytes/s

The number of bytes per second read and written across all disks

disk_write_bytes_details

bytes/s

The number of bytes per second written from the disks broken down by disk and type of operation (e.g., disk /dev/nvme01 and operation WRITE)

disk_read_bytes_details

bytes/s

The number of bytes per second read from the disks broken down by disk and type of operation (e.g., disk /dev/nvme01 and operation READ)

filesystem_util

percent

The space utilization % of filesystems broken down by type and device (e.g., filesystem of type overlayfs on device /dev/loop1)

filesystem_used

bytes

The amount of space used on the filesystems broken down by type and device (e.g., filesystem of type zfs on device /dev/nvme01)

filesystem_size

bytes

The size of filesystems broken down by type and device (e.g., filesystem of type ext4 for device /dev/nvme01)

proc_blocked

processes

The number of processes blocked (e.g, for IO or swapping reasons)

os_context_switch

switches/s

The number of context switches per second

os_cpuSchedMinGranularity

2250000 ns

300000→30000000 ns

Minimal preemption granularity (in nanoseconds) for CPU bound tasks

os_cpuSchedWakeupGranularity

3000000 ns

400000→40000000 ns

Scheduler Wakeup Granularity (in nanoseconds)

os_CPUSchedMigrationCost

500000 ns

100000→5000000 ns

Amount of time (in nanoseconds) after the last execution that a task is considered to be "cache hot" in migration decisions. A "hot" task is less likely to be migrated to another CPU, so increasing this variable reduces task migrations

os_CPUSchedChildRunsFirst

0

0→1

A freshly forked child runs before the parent continues execution

os_CPUSchedLatency

18000000 ns

2400000→240000000 ns

Targeted preemption latency (in nanoseconds) for CPU bound tasks

os_CPUSchedAutogroupEnabled

1

0→1

Enables the Linux task auto-grouping feature, where the kernel assigns related tasks to groups and schedules them together on CPUs to achieve higher performance for some workloads

os_CPUSchedNrMigrate

32

3→320

Scheduler NR Migrate

os_MemorySwappiness

1

0→100

Memory Swappiness

os_MemoryVmVfsCachePressure

100 %

10→100 %

VFS Cache Pressure

os_MemoryVmMinFree

67584 KB

10240→1024000 KB

Minimum Free Memory

os_MemoryVmDirtyRatio

20 %

1→99 %

When the dirty memory pages exceed this percentage of the total memory, processes are forced to write dirty buffers during their time slice instead of continuing to write

os_MemoryVmDirtyBackgroundRatio

10 %

1→99 %

When the dirty memory pages exceed this percentage of the total memory, the kernel begins to write them asynchronously in the background

os_MemoryTransparentHugepageEnabled

never

always never madvise

Transparent Hugepage Enablement

os_MemoryTransparentHugepageDefrag

always

always never madvise defer defer+madvise

Transparent Hugepage Enablement Defrag

os_MemorySwap

swapon

swapon swapoff

Memory Swap

os_MemoryVmDirtyExpire

3000 centisecs

300→30000 centisecs

Memory Dirty Expiration Time

os_MemoryVmDirtyWriteback

500 centisecs

50→5000 centisecs

Memory Dirty Writeback

os_NetworkNetCoreSomaxconn

128 connections

12→1200 connections

Network Max Connections

os_NetworkNetCoreNetdevMaxBacklog

1000 packets

100→10000 packets

Network Max Backlog

os_NetworkNetIpv4TcpMaxSynBacklog

512 packets

52→15120 packets

Network IPV4 Max Sync Backlog

os_NetworkNetCoreNetdevBudget

300 packets

30→3000 packets

Network Budget

os_NetworkNetCoreRmemMax

212992 bytes

21299→2129920 bytes

Maximum network receive buffer size that applications can request

os_NetworkNetCoreWmemMax

21299→2129920 bytes

21299→2129920 bytes

Maximum network transmit buffer size that applications can request

os_NetworkNetIpv4TcpSlowStartAfterIdle

1

0→1

Network Slow Start After Idle Flag

os_NetworkNetIpv4TcpFinTimeout

60

6 →600 seconds

Network TCP timeout

os_NetworkRfs

0

0→131072

If enabled increases datacache hitrate by steering kernel processing of packets to the CPU where the application thread consuming the packet is running

os_StorageReadAhead

128 KB

0→1024 KB

Read-ahead speeds up file access by pre-fetching data and loading it into the page cache so that it can be available earlier in memory instead of from disk

os_StorageNrRequests

1000 packets

100→10000 packets

Network Max Backlog

os_StorageRqAffinity

1

1→2

Storage Requests Affinity

os_StorageQueueScheduler

none

none kyber mq-deadline bfq

Storage Queue Scheduler Type

os_StorageNomerges

0

0→2

Enables the user to disable the lookup logic involved with IO merging requests in the block layer. By default (0) all merges are enabled. With 1 only simple one-hit merges will be tried. With 2 no merge algorithms will be tried

os_StorageMaxSectorsKb

128 KB

32→128 KB

The largest IO size that the OS c