top shows only part of available physmem

[Bartosz Stec]

W dniu 2011-01-26 19:44, John Baldwin pisze:
> On Wednesday, January 26, 2011 1:04:02 pm Marco van Tol wrote:
>> On Wed, Jan 26, 2011 at 12:35:56PM -0500, John Baldwin wrote:
>>> On Wednesday, January 26, 2011 8:20:28 am Bartosz Stec wrote:
>>>> W dniu 2011-01-26 14:06, John Baldwin pisze:
>>>>> On Wednesday, January 26, 2011 7:20:34 am Bartosz Stec wrote:
>>>>>> Guys,
>>>>>>
>>>>>> could someone explain me this?
>>>>>>
>>>>>>       # sysctl hw.realmem
>>>>>>       hw.realmem: 2139029504
>>>>>>
>>>>>> top line shows:
>>>>>>
>>>>>>       Mem: 32M Active, 35M Inact, 899M Wired, 8392K Cache, 199M Buf, 58M Free
>>>>>>
>>>>>> 32+35+899+8+199+58 = 1231MB
>>>>>>
>>>>>> Shouldn't that sum to all available ram? Or maybe I'm reading it wrong?
>>>>>> This machine has indeed 2GB of ram on board and showed in BIOS.
>>>>>> i386  FreeBSD 8.2-PRERELEASE #16: Mon Jan 17 22:28:53 CET 2011
>>>>>> Cheers.
>>>>> First, don't include 'buf' as isn't a separate set of RAM, it is only a range
>>>>> of the virtual address space in the kernel.  It used to be relevant when the
>>>>> buffer cache was separate from the VM page cache, but now it is mostly
>>>>> irrelevant (arguably it should just be dropped from top output).
>>>> Thanks for the explanation. So 1231MB - 199MB Buf and we got about 1GB
>>>> of memory instead of 2B.
>>>>
>>>>> However, look at what hw.physmem says (and the realmem and availmem lines in
>>>>> dmesg).  realmem is actually not that useful as it is not a count of the
>>>>> amount of memory, but the address of the highest memory page available.  There
>>>>> can be less memory available than that due to "holes" in the address space for
>>>>> PCI memory BARs, etc.
>>>>>
>>>> OK, here you go:
>>>> # sysctl hw | grep mem
>>>>
>>>>      hw.physmem: 2125893632
>>>>      hw.usermem: 1212100608
>>>>      hw.realmem: 2139029504
>>>>      hw.pci.host_mem_start: 2147483648
>>> Humm, you should still have 2GB of RAM then.  All the memory you set aside
>>> for ARC should be counted in the 'wired' count, so I'm not sure why you see
>>> 1GB of RAM rather than 2GB.
>> For what its worth (seems to be the same values top shows), the sysctl's
>> I use to make cacti graphs of memory usage are: (Counts are in pages)
>>
>> vm.stats.vm.v_page_size
>>
>> vm.stats.vm.v_wire_count
>> vm.stats.vm.v_active_count
>> vm.stats.vm.v_inactive_count
>> vm.stats.vm.v_cache_count
>> vm.stats.vm.v_free_count
>>
>> Using the output of those sysctls I allways get a cacti graph which at
>> least very much seems to account for all memory, and has a flat surface
>> in a stacked graph.
> These sysctls are exactly what top uses.  There is also a 'v_page_count'
> which is a total count of pages.
>
So here's additional sysctl output from now:

    fbsd# sysctl hw | grep mem
    hw.physmem: 2125893632
    hw.usermem: 1392594944
    hw.realmem: 2139029504
    hw.pci.host_mem_start: 2147483648

    fbsd# sysctl vm.stats.vm
    vm.stats.vm.v_kthreadpages: 0
    vm.stats.vm.v_rforkpages: 0
    vm.stats.vm.v_vforkpages: 1422927
    vm.stats.vm.v_forkpages: 4606557
    vm.stats.vm.v_kthreads: 40
    vm.stats.vm.v_rforks: 0
    vm.stats.vm.v_vforks: 9917
    vm.stats.vm.v_forks: 30429
    vm.stats.vm.v_interrupt_free_min: 2
    vm.stats.vm.v_pageout_free_min: 34
    vm.stats.vm.v_cache_max: 27506
    vm.stats.vm.v_cache_min: 13753
    vm.stats.vm.v_cache_count: 20312
    vm.stats.vm.v_inactive_count: 18591
    vm.stats.vm.v_inactive_target: 20629
    vm.stats.vm.v_active_count: 1096
    vm.stats.vm.v_wire_count: 179027
    vm.stats.vm.v_free_count: 6193
    vm.stats.vm.v_free_min: 3260
    vm.stats.vm.v_free_target: 13753
    vm.stats.vm.v_free_reserved: 713
    vm.stats.vm.v_page_count: 509752
    vm.stats.vm.v_page_size: 4096
    vm.stats.vm.v_tfree: 196418851
    vm.stats.vm.v_pfree: 2837177
    vm.stats.vm.v_dfree: 0
    vm.stats.vm.v_tcached: 1305893
    vm.stats.vm.v_pdpages: 3527455
    vm.stats.vm.v_pdwakeups: 187
    vm.stats.vm.v_reactivated: 83786
    vm.stats.vm.v_intrans: 3053
    vm.stats.vm.v_vnodepgsout: 134384
    vm.stats.vm.v_vnodepgsin: 29213
    vm.stats.vm.v_vnodeout: 96249
    vm.stats.vm.v_vnodein: 29213
    vm.stats.vm.v_swappgsout: 19730
    vm.stats.vm.v_swappgsin: 8573
    vm.stats.vm.v_swapout: 5287
    vm.stats.vm.v_swapin: 2975
    vm.stats.vm.v_ozfod: 83338
    vm.stats.vm.v_zfod: 2462557
    vm.stats.vm.v_cow_optim: 330
    vm.stats.vm.v_cow_faults: 1239253
    vm.stats.vm.v_vm_faults: 5898471

    fbsd# 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: 60)
    Virtual Memory:         (Total: 4971660K Active: 699312K)
    Real Memory:            (Total: 540776K Active: 29756K)
    Shared Virtual Memory:  (Total: 41148K Active: 19468K)
    Shared Real Memory:     (Total: 4964K Active: 3048K)
    Free Memory Pages:      105308K


    /usr/bin/top line: Mem: 4664K Active, 73M Inact, 700M Wired, 79M
    Cache, 199M Buf, 23M Free
    Sum (Without Buf): 879,5 MB

    So what are we looking at? Wrong sysctls/top output or maybe
    actually FreeBSD doesn't use all available RAM for some reason?
    Could it be hardware problem? Maybe I should provide some additional
    data?

-- 
Bartosz Stec