CentOS 8
This page describes the Optimization Pack for the component type CentOS 8.
Metrics
CPU
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)
Memory
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
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
Notice: you can use a device custom filter to monitor a specific disk with Prometheus. You can find more information on Prometheus queries and the %FILTERS% placeholder here: Prometheus provider and here: Prometheus provider metrics mapping.
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
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)
Other metrics
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
Parameters
CPU
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
Memory
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
Network
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
Storage
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
Constraints
There are no general constraints among RHEL 8 parameters.
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