head -r3418363: top -opid process list order is rather odd (top -Saopid example shown)
Yuri Pankov
yuripv at yuripv.net
Tue Dec 25 15:44:35 UTC 2018
Yuri Pankov wrote:
> Mark Millard wrote:
>>
>>
>> On 2018-Dec-24, at 13:49, Yuri Pankov <yuripv at yuripv.net> wrote:
>>
>>> Mark Millard wrote:
>>>> From my from=source head -r3418363 context, top with -opid does not
>>>> seem to sort in a coherent order, not time of process creation order
>>>> (either direction) and not in just-PID numeric order (either
>>>> direction). For example:
>>>>
>>>> PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND
>>>> 0 root 24 -16 - 0 368K swapin 1 0:00 0.00% [kernel]
>>>> 16 root 1 -16 - 0 16K - 3 0:00 0.00% [soaiod2]
>>>> 752 root 1 20 0 18M 18M select 1 0:07 0.01% /usr/sbin/ntpd -p /var/db/ntp/ntpd.pid -c /etc/ntp.conf -g
>>>> 800 root 1 20 0 11M 908K nanslp 1 0:01 0.00% /usr/sbin/cron -s
>>>> 1 root 1 20 0 9900K 132K wait 3 0:00 0.00% [init]
>>>> 17 root 1 -16 - 0 16K - 0 0:00 0.00% [soaiod3]
>>>> 2 root 1 -16 - 0 16K crypto 0 0:00 0.00% [crypto]
>>>> 18 root 1 -16 - 0 16K - 0 0:00 0.00% [soaiod4]
>>>> 850 root 1 20 0 13M 2756K wait 3 0:00 0.00% login [pam] (login)
>>>> 3 root 1 -16 - 0 16K crypto 0 0:00 0.00% [crypto returns 0]
>>>> 19 root 1 -16 - 0 16K mmcsd 0 0:25 0.00% [mmcsd0: mmc/sd card]
>>>> 643 root 1 20 0 11M 1124K select 2 0:01 0.00% /usr/sbin/syslogd -s
>>>> 4 root 1 -16 - 0 16K crypto 0 0:00 0.00% [crypto returns 1]
>>>> 20 root 1 -16 - 0 16K mmcsd 0 0:00 0.00% [mmcsd0boot0: mmc/sd]
>>>> 5 root 1 -16 - 0 16K crypto 0 0:00 0.00% [crypto returns 2]
>>>> 21 root 1 -16 - 0 16K mmcsd 0 0:00 0.00% [mmcsd0boot1: mmc/sd]
>>>> 6 root 1 -16 - 0 16K crypto 0 0:00 0.00% [crypto returns 3]
>>>> 22 root 3 -16 - 0 48K psleep 3 0:12 0.00% [pagedaemon]
>>>> 5270 root 1 20 0 14M 3780K CPU2 2 0:00 0.14% top -Saopid
>>>> 662 root 1 20 0 11M 680K select 0 0:00 0.00% /usr/sbin/rpcbind
>>>> 7 root 2 -16 - 0 32K - 0 0:00 0.00% [cam]
>>>> 23 root 1 -16 - 0 16K psleep 2 0:00 0.00% [vmdaemon]
>>>> 5255 root 1 20 0 12M 3092K wait 0 0:00 0.00% -sh (sh)
>>>> 8 root 1 -16 - 0 16K waitin 0 0:00 0.00% [sctp_iterator]
>>>> 24 root 3 -16 - 0 48K qsleep 3 0:12 0.01% [bufdaemon]
>>>> 712 root 1 52 0 12M 616K select 0 0:00 0.00% /usr/sbin/mountd -r
>>>> 9 root 1 -16 - 0 16K - 1 0:04 0.00% [rand_harvestq]
>>>> 25 root 1 20 - 0 16K vlruwt 0 0:04 0.00% [vnlru]
>>>> 10 root 1 -16 - 0 16K audit_ 0 0:00 0.00% [audit]
>>>> 26 root 1 16 - 0 16K syncer 0 1:45 0.00% [syncer]
>>>> 714 root 1 52 0 12M 728K select 3 0:00 0.00% nfsd: master (nfsd)
>>>> 11 root 4 155 ki31 0 64K CPU0 0 144.6H 397.09% [idle]
>>>> 235 root 1 20 0 11M 564K select 3 0:00 0.00% dhclient: system.syslog (dhclient)
>>>> 715 root 32 52 0 11M 1120K rpcsvc 3 0:00 0.00% nfsd: server (nfsd)
>>>> 12 root 18 -52 - 0 288K WAIT 2 2:29 1.43% [intr]
>>>> 412 root 1 20 0 10M 72K select 2 0:00 0.00% /sbin/devd
>>>> 796 root 1 52 0 20M 672K select 0 0:00 0.00% /usr/sbin/sshd
>>>> 13 root 3 -8 - 0 48K - 1 0:11 0.00% [geom]
>>>> 14 root 20 -68 - 0 320K - 0 0:02 0.00% [usb]
>>>> 238 root 1 52 0 12M 416K select 1 0:00 0.00% dhclient: awg0 [priv] (dhclient)
>>>> 15 root 1 -16 - 0 16K - 0 0:00 0.00% [soaiod1]
>>>> 239 _dhcp 1 20 0 12M 484K select 1 0:00 0.00% dhclient: awg0 (dhclient)
>>>>
>>>> (Basically the Pine64+ 2GB [aarch64] above was idle after boot other than
>>>> some runs of top.)
>>>>
>>>> I see this oddity across architectures, for example amd64, powerpc64,
>>>> aarch64, armv7.
>>>
>>> No wonder, it doesn't seem to have worked ever (?) as the compare_pid is
>>> simply not defined in compares list. Try attached patch.
>>> <top.diff>
>>
>> I'm a long term top user and it used to work. For example, when I was running
>> head -r340287 it worked as I remember. (I recreated such a vintage recently
>> for a test of something else. The -opid ordering was coherent as I remember,
>> unlike the above.)
>>
>> It historically seemed to track the time order of process creation, even around the PID
>> number wrapping around. (So not a strict PID sort, at least for the PID shown.) This
>> was handy for monitoring buildworld buidkernel and port builds (all parallel).
>>
>> I'll probably try the patch when I have a chance, even if it does strict PID number
>> order. Thanks.
>
> OK, so top never did sort for '-opid' by itself, and rather relied on
> the process list to be sorted by birth time internally (as returned by
> kvm_getprocs()) and it doesn't seem to be really sorting by PID, more so
> when PID numbers wrap. Quick bisect shows that this behavior was
> changed by r340742 ("proc: implement pid hash locks and an iterator"),
> so I guess we now just need to implement real sorting by PID.
>
> I have attached another patch version adding pid comparison function
> done like the other ones.
And there's a differential adding both explicit PID sorting, as well as
sorting by birth time for those who'd like to have the previous behavior:
https://reviews.freebsd.org/D18658
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