Date: Fri, 10 Jun 2022 21:32:10 -0700 From: Mark Millard <marklmi@yahoo.com> To: FreeBSD Hackers <freebsd-hackers@freebsd.org> Cc: Daniel Ebdrup Jensen <debdrup@freebsd.org>, David Cross <david@crossfamilyweb.com>, Robert Clausecker <fuz@fuz.su> Subject: Re: What can I learn about data that is staying paged out? (There is a more specific poudriere bulk related context given.) Message-ID: <6EA27152-3355-4356-B246-A083F31452F2@yahoo.com> In-Reply-To: <573B8B0C-5209-459D-98AD-EE92DDA4DF83@yahoo.com> References: <C337A09C-D546-46FC-A166-DBB3237D1AFC@yahoo.com> <A9C9AC24-62EC-43C1-B713-F2012CD1FD5B@yahoo.com> <573B8B0C-5209-459D-98AD-EE92DDA4DF83@yahoo.com>
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On 2022-Jun-10, at 21:27, Mark Millard <marklmi@yahoo.com> wrote:
> On 2022-Jun-5, at 15:04, Mark Millard <marklmi@yahoo.com> wrote:
>=20
>> On 2022-Jun-5, at 12:42, Mark Millard <marklmi@yahoo.com> wrote:
>>=20
>>> I have a poudriere bulk -a -c going on a 8 Gibyte
>>> aarch64 system. top has been showing an occasionally
>>> increasing swap usage but never any sizable decreases.
>>> Over 5800 ports have built so far. The context is UFS
>>> only. The system is running a non-debug build of main.
>>>=20
>>> Part of the context is ( in /etc/sysctl.conf ):
>>>=20
>>> vm.swap_enabled=3D0
>>> vm.swap_idle_enabled=3D0
>>>=20
>>> Also ( in /usr/local/etc/poudriere.conf ):
>>>=20
>>> USE_TMPFS=3D"data"
>>>=20
>>> poudriere's TMPFS reports normally total under 128
>>> KiBytes across the 4 builders.
>>>=20
>>> For reference, example figures . . .
>>>=20
>>> A top variant shows:
>>>=20
>>> Swap: 30720Mi Total, 306816Ki Used
>>>=20
>>> vmstat -s shows:
>>>=20
>>> 78152 swap pager pages paged out
>>>=20
>>> Note: (78152*4096)/1024 =3D=3D 312608Ki
>>>=20
>>> So nearly all of the "swap pager pages paged out"
>>> pages are still sitting out in the used swap/paging
>>> space. Thus, the usage is not held by user processes
>>> or is held via very long running processes or is
>>> not directly tied to user processes --or some mix.
>>>=20
>>> The variant of top reports never having observed
>>> more than: 6658Mi MaxObs(Act+Wir+Lndry).
>>> ("MaxObs" is short for "Maximum Observed".)
>>> Such high usage is for a bounded time, long past
>>> at this point. (Until some combination of port
>>> builds ends up active that uses such.)
>>>=20
>>> So I'm curious:
>>>=20
>>> What can I learn about the data that is staying
>>> paged out (and is gradually growing)? How can I
>>> learn it?
>>>=20
>>>=20
>>> Other notes:
>>>=20
>>> The poudriere jail being built is:
>>>=20
>>> # poudriere jail -jmain-CA7-bulk_a -i
>>> Jail name: main-CA7-bulk_a
>>> Jail version: 14.0-CURRENT
>>> Jail arch: arm.armv7
>>> Jail method: null
>>> Jail mount: /usr/obj/DESTDIRs/main-CA7-poud-bulk_a
>>> Jail fs: =20
>>> Jail updated: 2022-05-23 02:21:24
>>> Jail pkgbase: disabled
>>>=20
>>> (Just in case the armv7 jail usage or the null method
>>> or such is important to the issue.)
>>=20
>> Hmm. systat -swap reports a toal for the Devices/Paths Used
>> that is somewhat less than the total for what reports for the
>> Pid . . . Total figures (not the Pid Swap figures!):
>>=20
>> # systat -swap
>> /0 /1 /2 /3 /4 /5 /6 /7 /8 /9 =
/10
>> Load Average |||||||| =20
>>=20
>> Device/Path Size Used |0% /10 /20 /30 /40 / 60\ 70\ 80\ =
90\ 100|
>> gpt/CA72USBswp14 14G 150M
>> gpt/CA72USBswp16 16G 150M
>> Total 30G 300M
>>=20
>> Pid Username Command Swap/Total Per-Process Per-System
>> 1453 root nfsd 1M / 15M 9% 0%
>> 1451 root mountd 1M / 15M 7% 0%
>> 1481 root sshd 912K / 20M 4% 0%
>> 1406 root ntpd 740K / 27M 2% 0%
>> 1513 root login 724K / 14M 5% 0%
>> 1514 root sh 656K / 13M 4% 0%
>> 342 _dhcp dhclient 516K / 13M 3% 0%
>> 1363 root rpcbind 448K / 13M 3% 0%
>> 1454 root nfsd 400K / 12M 3% 0%
>> 341 root dhclient 380K / 13M 2% 0%
>> 1341 root syslogd 324K / 12M 2% 0%
>> 1505 root getty 292K / 12M 2% 0%
>> 1510 root getty 292K / 12M 2% 0%
>> 1511 root getty 292K / 12M 2% 0%
>> 1512 root getty 292K / 12M 2% 0%
>> 1509 root getty 292K / 12M 2% 0%
>> 1508 root getty 292K / 12M 2% 0%
>> 1507 root getty 292K / 12M 2% 0%
>> 1506 root getty 288K / 12M 2% 0%
>> 1135 root devd 272K / 11M 2% 0%
>> 338 root dhclient 264K / 13M 2% 0%
>> 1 root init 244K / 11M 2% 0%
>> 1486 root cron 188K / 13M 1% 0%
>>=20
>> I'm, Still looking for a clear indication of what
>> most of the 300 MiBytes or so of swap/paging space
>> is in use for.
>=20
> I finally gave up and checked if a swapoff would
> actually bring in all the pages from swap space
> that were needed (if any) and then un-configure
> the swap space. It did. (The bulk -a was still
> ongoing. It was not doing memory-hog builder
> activity at the time.)
>=20
> So such an activity may be a workaround for long
> running things like bulk -a to avoid a swap space
> accumulation that seems to be happening.
>=20
> I do not know how much was brought in to RAM vs.
> simply deallocated from swap space (pages not
> changed and still in RAM). If I do such a test
> again, it would be good to figure out how to
> monitor what the swapoff does for bringing in
> pages vs. just discarding them --if possible.
>=20
> After a while 12136Ki Used showed up after the
> swapon that reconfigured the swap space, which is
> about the size of the increments that I'd observed
> for its sustained increases.
>=20
An interesting point for "systat -swap" now:
/0 /1 /2 /3 /4 /5 /6 /7 /8 /9 =
/10
Load Average |||||||||||||||||||||||||||||
Device/Path Size Used |0% /10 /20 /30 /40 / 60\ 70\ 80\ =
90\ 100|
gpt/CA72USBswp14 14G 6108K
gpt/CA72USBswp16 16G 6028K
Total 30G 12M
Pid Username Command Swap/Total Per-Process Per-System
No process is listed as using swap but the 12M
shows as used! That should be a hint, not that
it is directly useful for me figuring out what
the usage is from/for.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
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