Processes are incorrectly marked as swapped out

[Andy Farkas]

On 29/01/14 02:42, John Baldwin wrote:
> On Thursday, January 23, 2014 8:02:29 am Ronald Klop wrote:
>> On Thu, 23 Jan 2014 13:19:36 +0100, Dmitry Sivachenko
>> <trtrmitya at gmail.com> wrote:
>>
>>> Hello!
>>>
>>> After upgrade from stable/9 to stable/10 I see the following regression.
>>> Some processes are marked as swapped out in top(1) output:
>>>
>>>   1436 root            1  43    0 16524K     0K nanslp 14   1:14   0.00%
>>> <cron>
>>>   1381 smmsp           1  20    0 23988K     0K pause  18   0:04   0.00%
>>> <sendma
>>> 99348 mitya           1  21    0 23492K     0K pause  16   0:00   0.00%
>>> <csh>
>>>
>>> ps(1) also shows them as swapped out (W as second character in state
>>> field):
>>>   1381  -  IWs       0:00.00 sendmail: Queue runner at 00:30:00 for
>>> /var/spool/clie
>>>   1436  -  IWs       0:00.00 /usr/sbin/cron -s
>>> 80231  -  IWs       0:00.00 /usr/local/sbin/collectdmon -c
>>> /usr/local/sbin/coll
>>> 99348  1  IWs       0:00.00 -csh (csh)
>>>
>>> Though swapinfo reports that zero swap is used and even if I turn swap
>>> completely off (swapoff -a)
>>> the output of both top(1) and ps(1) does not change: these processes are
>>> still marked as swapped out.
>> The code of an application can get removed from memory, because there
>> still is an image of it in the executable on disk. It can be 'swapped' in
>> by reading the executable again. The program is memory mapped (mmap).
>> See VN PAGER vs SWAP PAGER in 'systat -vm'.
> However, a swapped out process always uses swap (for kernel stacks), so this
> seems like a real bug.
>

Probably not related, but on a VirtualBox VM guest running:

FreeBSD 10.0-STABLE (GENERIC) #0 r261215: Tue Jan 28 18:13:37 EST 2014

having been freshly rebooted:

% uptime
  7:59AM  up 43 secs, 2 users, load averages: 0.79, 0.30, 0.11

I see this strange anomaly in the "TIME" column of top(1):

% top -CHSb -otime | grep swap
     0 root       -16    0     0K   160K swapin  0  47.8H   0.00% 
kernel{swapper}

No swap is being used (of ~3GB). Filesystem is UFS.

Possibly a formatting error although earlier values have been 45.4H & 47.2H
with reboots in between.

-andyf