Re: snmp oid for memory usage, vmstat -i and others

Hi Yuri

Thanks for your reply!

So, I can find total memory via HOST-RESOURCES-MIB::hrMemorySize.0

But how to calculate used memory?  I guess I need to find all
HOST-RESOURCES-MIB::hrStorageType = HOST-RESOURCES-TYPES::hrStorageRam 
and then multiply corresponding hrStorageAllocationUnits * hrStorageSize 
and sum all of them.

Is it correct?


On 25.01.2022 08:32, Yuri wrote:
> Yuri wrote:
>> Victor Gamov wrote:
>>> Hi All
>>>
>>> Some questions about bsnmpd.
>>>
>>> Is it possible to get memory usage via bsnmpd?  When I tried to get
>>> something like "snmpget hrStorageDescr.1 hrStorageAllocationUnits.1
>>> hrStorageSize.1 hrStorageUsed.1" then I've got this values:
>>>
>>> =====
>>> HOST-RESOURCES-MIB::hrStorageDescr.1 = STRING: Real Memory Metrics
>>> HOST-RESOURCES-MIB::hrStorageAllocationUnits.1 = INTEGER: 4096 Bytes
>>> HOST-RESOURCES-MIB::hrStorageSize.1 = INTEGER: 391488
>>> HOST-RESOURCES-MIB::hrStorageUsed.1 = INTEGER: 391252
>>> =====
>>>
>>> How I must process it to calculate actual memory usage for machine with
>>> 4GB RAM and without swap?
>>>
>>> =====
>>> $ sysctl hw | egrep 'hw.(phys|user|real)'
>>> hw.physmem: 4243894272
>>> hw.usermem: 3580182528
>>> hw.realmem: 4294967296
>>> =====
>>
>> Values returned by bsnmpd look weird to me as well, so I looked into it
>> a bit.  Excerpt from the snmp_hostres (as a standalone test case):
>> ----
>> #include <sys/types.h>
>> #include <sys/sysctl.h>
>> #include <sys/vmmeter.h>
>>
>> #include <vm/vm_param.h>
>>
>> #include <err.h>
>> #include <stdio.h>
>>
>> static struct vmtotal mem_stats;
>>
>> int
>> main(void)
>> {
>>          int mib[2] = { CTL_VM, VM_TOTAL };
>>          size_t len = sizeof(mem_stats);
>>
>>          if (sysctl(mib, 2, &mem_stats, &len, NULL, 0) != 0)
>>                  err(1, "sysctl");
>>
>>          printf("real=%lu\n", mem_stats.t_rm);
>>
>>          return (0);
>> }
>> ----
>> output:
>> real=31632
>> ----
>>
>> Now the sysctl output:
>> ----
>> $ sysctl vm.vmtotal
>> vm.vmtotal:
>> System wide totals computed every five seconds: (values in kilobytes)
>> ===============================================
>> Processes:              (RUNQ: 1 Disk Wait: 0 Page Wait: 0 Sleep: 28)
>> Virtual Memory:         (Total: 547240K Active: 542480K)
>> Real Memory:            (Total: 126572K Active: 125600K)
>> Shared Virtual Memory:  (Total: 4612K Active: 0K)
>> Shared Real Memory:     (Total: 924K Active: 0K)
>> Free Memory:    3608396K
>> ---
>> I can't map the output to anything on the system (16G RAM, 16G swap)
>> except for the "Free Memory", it matches.
>>
>> 31632 ("real") * 4096 ("pagesize") matches the "Real Memory" in sysctl
>> output.  Though to get anything resembling 16G, "real" needs to be
>> multiplied by 512 (K?).
>>
>> As a wild guess, it seems that the units used are wrong here, or I
>> simply don't understand the meaning of these values.
> 
> Looking at sys/vmmeter.h, my assumptions above are wrong:
> 
> uint64_t        t_rm;           /* total real memory in use */
> 
> But that does not include the "wired" (and other) pages, so I'm not sure
> about this metric usefulness.
> 
> In any case, you have the following:
> 
> HOST-RESOURCES-MIB::hrMemorySize.0 = INTEGER: 16734232 KBytes
> 

-- 
CU,
Victor Gamov