Re: More intelligent swap monitoring?

[Lutz Mader]

Hello Jamie,
this is a simple tgz Package, feel free to unpack the package and copy
the bin/monit file to a proper place. But keep in mind, this is a test
package only, based on Monit 5.35.0 for Linux x86_64.

> That's brilliant - thank you very much.

The official fix will became available with 5.36.0, maybe.

The data should be similar to the data from "vmstat -s" and "vmstat 30"
(see your monitrc file, option "set daemon  30").

Keep in mind,
this is for testing/validation purpose only,
Lutz



Am 02.05.25 um 15:14 schrieb Jamie Burchell via This is the general
mailing list for monit:
> Hi Lutz
> 
> That's brilliant - thank you very much.
> 
> I'm currently using the version 5.33.0 from EPEL (Rocky Linux 9). How should
> I replace/install the test package?
> 
> Thanks in advance
> Jamie
> 
> -----Original Message-----
> From: monit-general-bounces+jamie=ib3.uk@nongnu.org
> <monit-general-bounces+jamie=ib3.uk@nongnu.org> On Behalf Of Lutz Mader
> Sent: 02 May 2025 02:11
> To: This is the general mailing list for monit <monit-general@nongnu.org>
> Subject: Re: More intelligent swap monitoring?
> 
> Sorry Jamie, I'm late.
> 
> Based on your suggestion I add a new test to "check system".
> 
> check system $HOST
> #  if memory usage > 75% then alert
> #  if swap usage > 25% then alert
>   if pagein > 10 pages then alert
>   if pageout > 20 pages then alert
>   if pagefault > 50 pages then alert
> 
> A test package is available from
> https://bitbucket.org/lutzmad/monit/downloads/monit-vmstat-suse12-x64.tar.gz
> 
> Let me know, if this will fix you problem,
> Lutz
> 
> Appendage:
> ~/bin/monit status slesbuild
> Monit 5.35.0 uptime: 20m
> 
> System 'slesbuild'
>   status                       OK
>   monitoring status            Monitored
>   monitoring mode              active
>   on reboot                    start
>   load average                 [0.00] [0.00] [0.05]
>   cpu                          0.4%usr 3.3%sys 0.0%nice 2.1%iowait
> 0.0%hardirq 0.0%softirq 0.0%steal 0.0%guest 0.0%guestnice
>   memory usage                 492.2 MB [27.4%]
>   swap usage                   8.0 MB [0.4%]
>   pagein count                 0 [58]
>   pageout count                0 [2050]
>   uptime                       5h 0m
>   boot time                    Thu, 01 May 2025 21:02:12
>   filedescriptors              3264 [1.8% of 180992 limit]
>   data collected               Fri, 02 May 2025 02:03:04
> 
> 
> Am 17.01.25 um 11:51 schrieb Jamie Burchell via This is the general
> mailing list for monit:
>> Hello
>>
>> I have reduced the amount of memory one of the services was consuming,
>> which
>> has abated the problem for now. However, there's still some swap being
>> used
>> so perhaps in a few days time the problem will come up again.
>>
>> Here's the output of /proc/meminfo as requested
>>
>> MemTotal:        7868472 kB
>> MemFree:          671568 kB
>> MemAvailable:    3261880 kB
>> Buffers:               0 kB
>> Cached:           893768 kB
>> SwapCached:        47448 kB
>> Active:          2661256 kB
>> Inactive:        1320396 kB
>> Active(anon):    2400964 kB
>> Inactive(anon):   800724 kB
>> Active(file):     260292 kB
>> Inactive(file):   519672 kB
>> Unevictable:        3072 kB
>> Mlocked:               0 kB
>> SwapTotal:       4194300 kB
>> SwapFree:        3923228 kB
>> Zswap:                 0 kB
>> Zswapped:              0 kB
>> Dirty:                32 kB
>> Writeback:             0 kB
>> AnonPages:       3003564 kB
>> Mapped:           169140 kB
>> Shmem:            113804 kB
>> KReclaimable:    2124156 kB
>> Slab:            2540272 kB
>> SReclaimable:    2124156 kB
>> SUnreclaim:       416116 kB
>> KernelStack:       13712 kB
>> PageTables:        77444 kB
>> SecPageTables:         0 kB
>> NFS_Unstable:          0 kB
>> Bounce:                0 kB
>> WritebackTmp:          0 kB
>> CommitLimit:     8128536 kB
>> Committed_AS:   12257916 kB
>> VmallocTotal:   34359738367 kB
>> VmallocUsed:       31016 kB
>> VmallocChunk:          0 kB
>> Percpu:             1840 kB
>> HardwareCorrupted:     0 kB
>> AnonHugePages:   1378304 kB
>> ShmemHugePages:        0 kB
>> ShmemPmdMapped:        0 kB
>> FileHugePages:         0 kB
>> FilePmdMapped:         0 kB
>> CmaTotal:              0 kB
>> CmaFree:               0 kB
>> Unaccepted:            0 kB
>> HugePages_Total:       0
>> HugePages_Free:        0
>> HugePages_Rsvd:        0
>> HugePages_Surp:        0
>> Hugepagesize:       2048 kB
>> Hugetlb:               0 kB
>> DirectMap4k:      118624 kB
>> DirectMap2M:     8269824 kB
>>
>> Regards
>> Jamie
>>
>>
>> --
>>
>>
>> -----Original Message-----
>> From: monit-general-bounces+jamie=ib3.co.uk@nongnu.org
>> <monit-general-bounces+jamie=ib3.co.uk@nongnu.org> On Behalf Of Lutz Mader
>> Sent: 15 January 2025 20:37
>> To: This is the general mailing list for monit <monit-general@nongnu.org>
>> Subject: Re: More intelligent swap monitoring?
>>
>> Hello,
>> I have no useful examples, vmstat swap usage is si=0 and so=0 only.
>> The values calculated based on /proc/meminfo fit, on a Linux system.
>>
>> And the system status information seems to be useful.
>>
>>> Is it possible to configure Monit to alert of actual swapping
>>> out rather than swap file usage, or am I barking up the wrong tree?
>>
>> You are right, monit does not show the actual swap file IO (page in/out
>> data), the data based on the usage.
>>
>> monit status LINUX
>> Monit 5.34.0 uptime: 49d 0h 43m
>>
>> System 'LINUX'
>>   status                       OK
>>   monitoring status            Monitored
>>   monitoring mode              active
>>   on reboot                    start
>>   load average                 [7.30] [8.60] [12.77]
>>   cpu                          0.8%usr 0.3%sys 14.7%nice 0.0%iowait
>> 0.0%hardirq 0.0%softirq 0.0%steal 0.0%guest 0.0%guestnice
>>   memory usage                 42.6 GB [11.3%]
>>   swap usage                   10.4 MB [0.5%]
>>   uptime                       61d 19h 43m
>>   boot time                    Thu, 14 Nov 2024 14:54:46
>>   filedescriptors              16800 [0.2% of 6815744 limit]
>>   data collected               Wed, 15 Jan 2025 10:37:52
>>
>> The vmstat data.
>>
>> Swap
>> si: Amount of memory swapped in from disk (/s).
>> so: Amount of memory swapped to disk (/s).
>>
>> vmstat
>> procs -----------memory---------- ---swap-- -----io---- -system--
>> ------cpu-----
>> r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy
>> id wa st
>> 7  0  10624 273713168 811688 87684144    0    0    69    40    0    0 11
>>  1 88  0  0
>>
>> vmstat -s
>>     395130516 K total memory
>>     120558732 K used memory
>>      90364732 K active memory
>>      11131200 K inactive memory
>>     274571784 K free memory
>>        811824 K buffer memory
>>      88984004 K swap cache
>>       2095100 K total swap
>>         10624 K used swap
>>       2084476 K free swap
>>    1313872869 non-nice user cpu ticks
>>    1427185498 nice user cpu ticks
>>     247910673 system cpu ticks
>>   22633904247 idle cpu ticks
>>       6802373 IO-wait cpu ticks
>>             0 IRQ cpu ticks
>>       2608560 softirq cpu ticks
>>             0 stolen cpu ticks
>>   17687866581 pages paged in
>>   10300491953 pages paged out
>>          1345 pages swapped in
>>          6655 pages swapped out
>>    3444460676 interrupts
>>     416044891 CPU context switches
>>    1731592487 boot time
>>     273618695 forks
>>
>> The values based on /proc/meminfo.
>>
>> cat /proc/meminfo
>> MemTotal:       395130516 kB
>> MemFree:        275604548 kB
>> MemAvailable:   353323016 kB
>> Buffers:          811800 kB
>> Cached:         85849340 kB
>> SwapCached:          892 kB
>> Active:         89256636 kB
>> Inactive:       11124384 kB
>> Active(anon):   18733260 kB
>> Inactive(anon):  3398376 kB
>> Active(file):   70523376 kB
>> Inactive(file):  7726008 kB
>> Unevictable:      975348 kB
>> Mlocked:          975348 kB
>> SwapTotal:       2095100 kB
>> SwapFree:        2084476 kB
>> Dirty:               468 kB
>> Writeback:             0 kB
>> AnonPages:      14695184 kB
>> Mapped:          2965708 kB
>> Shmem:           8423756 kB
>> Slab:            8029800 kB
>> SReclaimable:    2699580 kB
>> SUnreclaim:      5330220 kB
>> KernelStack:       70320 kB
>> PageTables:       421232 kB
>> NFS_Unstable:          0 kB
>> Bounce:                0 kB
>> WritebackTmp:          0 kB
>> CommitLimit:    199660356 kB
>> Committed_AS:   26151808 kB
>> VmallocTotal:   34359738367 kB
>> VmallocUsed:           0 kB
>> VmallocChunk:          0 kB
>> HardwareCorrupted:     0 kB
>> AnonHugePages:         0 kB
>> ShmemHugePages:        0 kB
>> ShmemPmdMapped:        0 kB
>> HugePages_Total:       0
>> HugePages_Free:        0
>> HugePages_Rsvd:        0
>> HugePages_Surp:        0
>> Hugepagesize:       2048 kB
>> DirectMap4k:    37410524 kB
>> DirectMap2M:    286273536 kB
>> DirectMap1G:    80740352 kB
>>
>> The values are used to calculate the monit swap data.
>>
>> in src/process/sysdep_LINUX.c
>>
>> used_system_memory_sysdep(SystemInfo_T *si)
>>
>>         // Swap
>>         if (! (ptr = strstr(buf, "SwapTotal:")) || sscanf(ptr + 10,
>> "%llu", &swap_total) != 1) {
>>                 Log_error("system statistic error -- cannot get swap
>> total amount\n");
>>                 goto error;
>>         }
>>         if (! (ptr = strstr(buf, "SwapFree:")) || sscanf(ptr + 9,
>> "%llu", &swap_free) != 1) {
>>                 Log_error("system statistic error -- cannot get swap
>> free amount\n");
>>                 goto error;
>>         }
>>         si->swap.size = swap_total * 1024;
>>         si->swap.usage.bytes = (swap_total - swap_free) * 1024;
>>
>> The question is,
>> how does the /proc/meminfo output data look like on your system.
>>
>> Are some examples available, based on vmstat and the /proc/meminfo data.
>>
>> Lutz
>>
>>
>> Am 14.01.25 um 12:10 schrieb Jamie Burchell via This is the general
>> mailing list for monit:
>>> Hi
>>>
>>>
>>>
>>> I currently use Monit to alert me if swap usage is over > 20%. This works
>>> most of the time, but I have a particularly stubborn VM currently which
>>> appears to like to add data to swap and then not touch it. Using vmstat
>>> shows there are either no, or maybe the odd non-zero swap in operation
>>> and
>>> no swap outs. Is it possible to configure Monit to alert of actual
>>> swapping
>>> out rather than swap file usage, or am I barking up the wrong tree?
>>>
>>>
>>>
>>> Thanks in advance!
>>>
>>> Jamie
>>>
>>
>>
> 
>