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SapMachine Vitals
Thomas Stuefe edited this page Sep 2, 2022
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SapMachine Vitals is a monitoring facility for the SapMachine. It keeps a long-term log of system- and VM metrics considered vital (hence the name).
Vitals periodically poll the VM and the operating system for essential ("vital") data. Per default, this happens every ten seconds.
These data samples are kept in a short-term high-resolution buffer for an hour; after that period, they are downsampled to a long-term low-resolution buffer that spans ten days.
The Vitals are very frugal in terms of memory and CPU costs:
- memory overhead about 300KB
- performance overhead, with the normal sample interval of 10 seconds, is not measurable (we really tried).
Since they are so low-cost, they are enabled in the SapMachine by default.
------------system------------
avail: Memory available without swapping [host]
comm: Committed memory [host]
crt: Committed-to-Commit-Limit ratio (percent) [host]
swap: Swap space used [host]
si: Number of pages swapped in [host] [delta]
so: Number of pages pages swapped out [host] [delta]
p: Number of processes
t: Number of threads
tr: Number of threads running
tb: Number of threads blocked on disk IO
cpu-us: CPU user time [host]
cpu-sy: CPU system time [host]
cpu-id: CPU idle time [host]
cpu-st: CPU time stolen [host]
cpu-gu: CPU time spent on guest [host]
cgroup-lim: cgroup memory limit [cgrp]
cgroup-slim: cgroup memory soft limit [cgrp]
cgroup-usg: cgroup memory usage [cgrp]
cgroup-kusg: cgroup kernel memory usage (cgroup v1 only) [cgrp]
-----------process------------
virt: Virtual size
rss-all: Resident set size, total
rss-anon: Resident set size, anonymous memory [krn]
rss-file: Resident set size, file mappings [krn]
rss-shm: Resident set size, shared memory [krn]
swdo: Memory swapped out
cheap-usd: C-Heap, in-use allocations [glibc]
cheap-free: C-Heap, bytes in free blocks [glibc]
cpu-us: Process cpu user time
cpu-sy: Process cpu system time
io-of: Number of open files
io-rd: IO bytes read from storage or cache
io-wr: IO bytes written
thr: Number of native threads
-------------jvm--------------
heap-comm: Java Heap Size, committed
heap-used: Java Heap Size, used
meta-comm: Meta Space Size (class+nonclass), committed
meta-used: Meta Space Size (class+nonclass), used
meta-csc: Class Space Size, committed [cs]
meta-csu: Class Space Size, used [cs]
meta-gctr: GC threshold
code: Code cache, committed
nmt-mlc: Memory malloced by hotspot [nmt]
nmt-map: Memory mapped by hotspot [nmt]
nmt-gc: NMT "gc" (GC-overhead, malloc and mmap) [nmt]
nmt-oth: NMT "other" (typically DBB or Unsafe.allocateMemory) [nmt]
nmt-ovh: NMT overhead [nmt]
jthr-num: Number of java threads
jthr-nd: Number of non-demon java threads
jthr-cr: Threads created [delta]
jthr-st: Total reserved size of java thread stacks [nmt] [linux]
cldg-num: Classloader Data
cldg-anon: Anonymous CLD
cls-num: Classes (instance + array)
cls-ld: Class loaded [delta]
cls-uld: Classes unloaded [delta]
[host]: values are host-global (not containerized).
[cgrp]: if containerized or running in systemd slice
[krn]: depends on kernel version
[glibc]: only shown for glibc-based distros
[delta]: values refer to the previous measurement.
[nmt]: only shown if NMT is available and activated
[cs]: only shown on 64-bit if class space is active
[linux]: only on Linux
(Vitals version 220600, pid: 18158)
Last 60 minutes:
-----------------------------------system ----------------------------------- -----------------------------process----------------------------- -----------------------------------jvm------------------------------------
------cpu------ ------cgroup------ --------rss--------- --cheap-- -cpu- -----io------ --heap--- ---------meta---------- ---jthr--- --cldg-- ------cls------
avail comm crt swap si so p t tr tb us sy id st gu lim slim usg kusg virt all anon file shm swdo usd free us sy of rd wr thr comm used comm used csc csu gctr code num nd cr num anon num ld uld
2022-06-17 17:04:43 56,0g 17,6g 52 0k 0 0 570 1683 2 0 6 0 93 0 0 9,3g 247m 14,3g 1,8g 1,8g 58m 100k 0k 138m 392m 6 0 135 6m 38m 94 1,1g 517m 120m 117m 14m 13m 199m 66m 47 27 8 631 376 21456 10 0
2022-06-17 17:04:33 56,0g 17,9g 53 0k 0 0 570 1751 2 0 8 0 92 0 0 9,3g 247m 14,3g 1,8g 1,8g 58m 100k 0k 148m 393m 7 0 135 11m 112m 94 1,1g 737m 120m 117m 14m 13m 199m 65m 47 27 9 629 374 21446 15 0
2022-06-17 17:04:23 56,0g 18,1g 54 0k 0 0 571 1784 2 0 7 0 93 0 0 9,2g 247m 14,3g 1,8g 1,8g 58m 100k 0k 139m 394m 6 0 135 9m 36m 94 1,1g 440m 119m 117m 14m 13m 199m 64m 48 27 7 629 374 21431 32 0
2022-06-17 17:04:13 56,0g 18,1g 54 0k 0 0 570 1786 4 0 9 0 90 0 0 9,2g 246m 14,3g 1,9g 1,8g 58m 100k 0k 144m 390m 9 0 135 8m 62m 96 1,1g 677m 119m 116m 14m 13m 198m 63m 50 27 9 600 345 21399 4 0
2022-06-17 17:04:03 56,0g 17,8g 53 0k 0 0 570 1771 4 0 15 1 85 0 0 9,1g 243m 14,3g 1,7g 1,7g 58m 100k 0k 189m 353m 13 0 135 10m 40m 96 998m 614m 119m 116m 14m 13m 198m 62m 50 27 12 600 345 21395 44 0
2022-06-17 17:03:53 56,2g 17,4g 52 0k 0 0 569 1721 2 0 8 0 92 0 0 8,9g 239m 14,3g 1,7g 1,6g 58m 100k 0k 134m 363m 7 0 135 5m 51m 94 998m 684m 118m 115m 14m 13m 197m 59m 48 27 10 600 345 21351 3 0
2022-06-17 17:03:43 56,3g 17,5g 52 0k 0 0 569 1703 3 0 5 0 94 0 0 8,8g 239m 14,3g 1,5g 1,5g 58m 100k 0k 141m 347m 5 0 136 142k 2m 94 868m 555m 118m 115m 14m 13m 196m 58m 48 27 1 600 345 21348 2 0
2022-06-17 17:03:33 56,3g 17,2g 51 0k 0 0 569 1681 4 0 5 0 94 0 0 8,8g 238m 14,3g 1,5g 1,5g 58m 100k 0k 122m 371m 5 0 136 148k 2m 93 868m 481m 118m 115m 14m 13m 196m 58m 47 27 0 600 345 21346 0 0
2022-06-17 17:03:23 56,4g 17,2g 51 0k 0 0 569 1675 2 0 5 0 95 0 0 8,7g 238m 14,3g 1,5g 1,5g 58m 100k 0k 120m 366m 4 0 136 153k 2m 93 868m 664m 118m 115m 14m 13m 196m 58m 47 27 0 600 345 21346 0 0
2022-06-17 17:03:13 56,4g 17,1g 51 0k 0 0 569 1665 2 0 7 0 93 0 0 8,7g 238m 14,3g 1,5g 1,5g 58m 100k 0k 126m 359m 6 0 135 7m 30m 93 868m 637m 118m 115m 14m 13m 196m 58m 47 27 4 600 345 21346 39 0
2022-06-17 17:03:03 56,5g 17,2g 51 0k 0 0 569 1675 5 0 8 0 91 0 0 8,6g 237m 14,3g 1,5g 1,4g 58m 100k 0k 164m 315m 7 0 135 270k 7m 101 868m 486m 117m 115m 14m 13m 192m 57m 55 27 14 598 345 21307 41 0
2022-06-17 17:02:53 56,5g 17,0g 50 0k 0 0 569 1653 4 0 13 1 87 0 0 8,6g 236m 14,3g 1,4g 1,4g 58m 100k 0k 192m 289m 12 0 135 15m 5m 98 868m 431m 116m 114m 14m 13m 192m 54m 52 27 15 598 345 21266 406 2
2022-06-17 17:02:43 57,0g 16,4g 49 0k 0 0 569 1639 1 0 3 1 97 0 0 8,1g 234m 14,3g 935m 877m 58m 100k 0k 148m 251m 2 0 135 8m 4m 82 354m 149m 113m 110m 14m 13m 168m 46m 47 27 28 577 329 20862 528 0
2022-06-17 17:02:33 57,1g 16,4g 49 0k 0 0 569 1672 1 0 0 0 100 0 0 8,0g 234m 14,3g 863m 806m 58m 0k 0k 111m 230m 0 0 140 138k <1k 114 354m 173m 108m 105m 13m 12m 168m 39m 80 60 0 563 315 20334 0 0
2022-06-17 17:02:23 57,1g 16,4g 49 0k 0 0 569 1675 1 0 0 0 100 0 0 8,0g 234m 14,3g 863m 806m 58m 0k 0k 111m 230m 0 0 139 137k 5k 117 354m 173m 108m 105m 13m 12m 168m 39m 83 61 0 563 315 20334 0 0
2022-06-17 17:02:13 57,1g 16,4g 49 0k 0 0 569 1673 1 0 0 0 99 0 0 8,0g 234m 14,3g 863m 806m 58m 0k 0k 111m 230m 0 0 138 128k <1k 117 354m 173m 108m 105m 13m 12m 168m 39m 83 61 0 563 315 20334 0 0
2022-06-17 17:02:03 57,1g 16,4g 49 0k 0 0 569 1673 1 0 1 0 99 0 0 8,0g 234m 14,3g 872m 814m 58m 0k 0k 115m 234m 0 0 138 158k 3m 118 354m 173m 108m 105m 13m 12m 168m 39m 84 61 4 563 315 20334 0 0
2022-06-17 17:01:53 57,1g 16,5g 49 0k 0 0 569 1682 1 0 0 0 100 0 0 8,0g 234m 14,3g 857m 799m 58m 68k 0k 113m 222m 0 0 137 214k <1k 119 354m 158m 108m 105m 13m 12m 168m 39m 85 62 2 563 315 20334 18 0
2022-06-17 17:01:43 57,1g 16,5g 49 0k 0 0 569 1690 1 0 3 1 95 0 0 8,0g 235m 14,3g 856m 799m 58m 68k 0k 112m 222m 3 1 136 5m 352k 119 354m 157m 108m 105m 13m 12m 168m 39m 84 60 152 563 315 20316 1688 2
2022-06-17 17:01:33 56,9g 17,0g 51 0k 0 0 569 1695 2 0 15 2 83 0 0 8,1g 235m 13,1g 1005m 948m 57m 68k 0k 161m 102m 15 1 137 115m 4m 104 768m 425m 98m 96m 12m 11m 101m 35m 69 22 89 494 264 18630 17907 3
2022-06-17 17:01:23 57,9g 16,3g 48 0k 569 1615 5 0 7,2g 230m 7,0g 37m 11m 25m 0k 0k 42m 2m 2 21 260m 5m 448k 266k 128k 8k 21m 7m 13 1 7 4 726
Vitals can be obtained with jcmd <pid> VM.vitals. Without options, a human-readable table is printed. Options include:
- output the report in CSV form to use in spreadsheets:
jcmd <pid> VM.vitals csv - one can specify the memory unit explicitly:
jcmd <pid> VM.vitals scale=M - by default, values are printed newest-to-oldest. Print order can be reversed, e.g. for CSV reports:
jcmd <pid> VM.vitals reverse CSV
The user can obtained also via command-line options -XX:+PrintVitalsAtExit or -XX:+DumpVitalsAtExit. The VM will print Vitals to stdout or to a file on shutdown. With -XX:+DumpVitalsAtExit, the file name can be overridden with -XX:VitalsFile=<filename>.
These switches are a convenient way to get metrics at the end of a java program, especially if it has a very short run time ("poor man's flight recorder").
Finally, Vitals are printed as part of error reports (hs_err_<pid>.log).
Vitals use Native Memory Tracking (NMT) for some of the more useful metrics. NMT is a JVM facility that tracks native memory usage. However, it adds some memory overhead and is therefore disabled by default.
If you use Vitals to track down native memory issues, we recommend enabling NMT with -XX:NativeMemoryTracking=summary.
| Option | Function |
|---|---|
-XX:(+-)EnableVitals |
Enable/disable Vitals. Note that since Vitals are enabled by default this switch can be used to explicitly disable them: -XX:-EnableVitals. |
-XX:(+-)PrintVitalsAtExit |
Prints Vitals to stdout upon (normal or abnormal) VM exit. |
-XX:(+-)DumpVitalsAtExit |
Dumps a Vitals report to a file upon (normal or abnormal) VM exit. The file will be written to the current directory and named sapmachine_vitals_.log. The location of the file can be overridden via -XX:VitalsFile.
|
-XX:VitalsFile=<filename> |
Specify the Vitals file path for -XX:+DumpVitalsAtExit. |
-XX:VitalsSampleInterval=<seconds> |
Override the Vitals sample interval. |
Vitals are a developer tool, mainly aimed at hotspot devs and support people; interpreting the values requires solid OS- and JVM knowledge (especially for memory management). Be careful what conclusions you draw from these numbers.
The metrics were selected for our support, hence heavily biased toward the typical problems plaguing our customers. Frequently these are high memory pressure scenarios; therefore, metrics include many memory data.
The columns are grouped into three (Linux) categories: "system" (host- or container-global values), "process" (process-local values) and "jvm". The Legend shown is pretty self-explanatory, but here are some of the most important columns:
| Column | Notes |
|---|---|
| heap-comm, heap-used | Java Heap Size, committed and used |
| meta-comm, meta-used | Total Metaspace size, committed and used. Note that this includes both Class space (if active) as well as non-class metaspace. As a rule of thumb, any value up to about 5-10KB per loaded class is okay. You can see the number of loaded classes in this table (column cls-num). Memory sizes larger than ~10KB per class may hint at excessive metaspace fragmentation. |
| meta-csc, meta-csu | This is the portion of metaspace reserved for class space. This seldom is a problem. |
| meta-gctr | Metaspace GC threshold. Often misunderstood: this is just a number. If committed total metaspace grows beyond this threshold, the VM will attempt a GC to clean out class loaders before allowing further metaspace growth. The badly misnamed VM parameter -XX:MetaspaceSize sets the initial value of the Metaspace GC threshold. |
| code | Committed code cache. |
| nmt-mlc | How much NMT thinks the VM did malloc(3). Only shows usage from within the hotspot, and only user payload sizes. It includes NMT overhead. It leaves out most usage from outside the hotspot. It also leaves out overhead from within the glibc, which can be significant. See also column cheap-usd and cheap-fre. |
| nmt-map | How much NMT thinks the VM did mmap(3) (committed). Includes committed portions of large areas like the java heap, code cache, and metaspace. |
| nmt-gc | How much the VM allocated for heap-related side structures (e.g. remembered set or card table). |
| nmt-oth | A high value here may indicate excessive DirectByteBuffer allocations. |
| nmt-ovh | NMT overhead. |
| jthr-num | number of java threads. |
| jthr-nd | Number of non-demon java threads. |
| jthr-cr | How many java threads were created since the last data sample (per default, in the last ten seconds). |
| jthr-st | Total committed size of java thread stacks. |
| cldg-num | Number of CLD structures; roughly translates to the number of class loaders (including loaders created due to reflection inflation, and for JDK<16 hidden loaders caused by Lambdas). |
| cls-num | Total number of classes |
| cls-ld, cls-uld | number of classes loaded/unloaded in the last ten seconds. High load-unload churns may increase Metaspace fragmentation, though this is less of a problem since JEP 387. |
| Column | Notes |
|---|---|
| virt | Virtual process size. Don't sweat this number. With modern kernels on 64-bit platforms, this value is meaningless unless you plan to use >128 TB heap. In particular, this memory size does not incur any real memory cost. |
| rss-all | RSS (resident set size). In combination with SWAP (swdo) this is the real footprint of the process you should be concerned about. |
| swdo | How much memory has this process swapped out. Ideally, this should be zero. |
| cheap-usd | How much memory this process has allocated via malloc(3) in the C-heap. This size includes allocations from all parts of the process, not just the hotspot, and also contains glibc-internal overhead. The overhead can be significant. Compared with nmt-mlc, this number can be much higher. Note: may be imprecise on glibc versions < 2.34. |
| cheap-fre | memory the process did free(3), but the glibc holds on for future use in the C-heap. If this is significant, it can be released manually with jcmd <pid> System.trim_native_heap, but be aware that doing so frequently may have performance costs. Note: may be imprecise on glibc versions < 2.34, or after a C-heap trim. |
| thr | number of native threads. This number includes threads not associated with the JVM. |
| Column | Notes |
|---|---|
| avail | How much memory is available on this host. Note that this shows the host value even when inside a container. |
| comm | How much memory the host has committed. The amount of committable memory is limited. It depends on the overcommit setting of the kernel (see https://www.kernel.org/doc/Documentation/vm/overcommit-accounting). On most machines, it is larger than the amount of physical memory but not endlessly, typically by a factor of 1.5. |
| crt | Commit ratio, in percent. A value of 100 means we have 100% of the committable memory committed. Higher values than 100 are possible if the system allows overcommit. |
| swap | Total swap space used on the host. |
| si, so | number of pages swapped in and out in the last ten seconds. High values here mean high swap activity. |
| p, t | Number of processes and threads on this host or inside the container. |
| cgroup-lim, cgroup-slim | The memory limit and the soft limit of the cgroup the process lives in. For cgroups v1, this is memory.limit_in_bytes and memory.soft_limit_in_bytes. For cgroups v2, this is "memory.max" and "memory.low". |
| cgroup-usg | Current memory usage (v1: "memory.usage_in_bytes", v2: "memory.current") of the containing cgroup. |
| cgroup-kusg | Current kernel memory usage of the cgroup. Only shown for v1. |