Re: 14.0-CURRENT failed to reclaim memory error in RPi 3B build

On Tue, Nov 8, 2022 at 11:25 AM Mark Millard <marklmi@yahoo.com> wrote:

> On Nov 7, 2022, at 18:40, Archimedes Gaviola <archimedes.gaviola@gmail.com>
> wrote:
>
> > . . .
> >
> > Hi Mark,
> >
> > With this set of build commands now,
> >
> > # cd /usr/src; make -j3 KERNCONF=ARM TARGET_ARCH=aarch64 buildworld
> kernel-toolchain buildkernel installworld installkernel distribution
> DESTDIR=/home/freebsd/rpi3b
> >
> > in RPi 3B, I encountered the other OOM error which is the 'thread waited
> too long to allocate a page'. This occurred from every build I conducted.
> Though the first error on 'failed to reclaim memory' was never experienced
> again. Below are the error logs.
> > ...
> > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 256929, size: 4096
> > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 3628, size: 4096
> > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 255839, size: 40960
> > pid 46153 (c++), jid 0, uid 0, was killed: a thread waited too long to
> allocate a page
> > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 255857, size: 28672
> > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 3634, size: 8192
> > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 256037, size: 4096
> > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 255320, size: 8192
> >
> > Perhaps some further tweaks are needed in the system so I set aside my
> RPi 3B temporarily and switched over to my RPi 4B using the same microSD
> card and USB flash drive (3.5 GB swap partition device) and the build
> completed successfully. It took around 30 hours to complete. This RPi 4B
> has 2GB RAM capacity while the RPi 3B has 1GB. From here, I'll continue
> looking further for system tunables in RPi 3B which has lesser RAM capacity.
>

Hi Mark,


> Given that you have added enough swap/paging
> space to avoid needing more:
>
> #
> # For plunty of swap/paging space (will not
> # run out), avoid pageout delays leading to
> # Out Of Memory killing of processes:
> vm.pfault_oom_attempts=-1
>
> With the above setting, if you did run out of
> swap/paging space and needed more, deadlocks
> would be possible as I understand. The above
> disables getting that type of OOM kill
> completely but, effectively, a deadlock is
> sort of a form of less-controlled kill.
>

Okay, confirmed the existing value is 3.

root@generic:~ # sysctl vm.pfault_oom_attempts
vm.pfault_oom_attempts: 3

and is writable as tested.

root@generic:~ # sysctl vm.pfault_oom_attempts=-1
vm.pfault_oom_attempts: 3 -> -1


> There is an alternative, but I've no clue how to
> find what values to set for any specific context.
> I just know the names and default values (as of
> when I last checked such defaults):
>
> #
> # For possibly insufficient swap/paging space
> # (might run out), increase the pageout delay
> # that leads to Out Of Memory killing of
> # processes (showing defaults at the time):
> #vm.pfault_oom_attempts= 3
> #vm.pfault_oom_wait= 10
> # (The multiplication is the total but there
> # are other potential tradoffs in the factors
> # multiplied, even for nearly the same total.)
>
> (Yes, one of those names is the same as was set
> to -1 in the earlier suggestion above. -1
> disables making attempts and just waits as long
> as it takes. That makes vm.pfault_oom_wait
> irrelevant in that kind of context.)
>
> As for where the settings can be placed . . .
>
> # sysctl -T vm.pfault_oom_attempts
> vm.pfault_oom_attempts: -1
>
> # sysctl -T vm.pfault_oom_wait
> vm.pfault_oom_wait: 10
>
> (So /boot/loader.conf is appropriate: loader tunables.)
>

Okay noted this.


>
> # sysctl -W vm.pfault_oom_attempts
> vm.pfault_oom_attempts: -1
>
> # sysctl -W vm.pfault_oom_wait
> vm.pfault_oom_wait: 10
>

Checking these values...

root@generic:~ # sysctl -T vm.pfault_oom_attempts
vm.pfault_oom_attempts: -1

root@generic:~ # sysctl -T vm.pfault_oom_wait
vm.pfault_oom_wait: 10


> (So /etc/sysctl.conf or the like is an alternative:
> Also writable.)
>

Okay this is noted.

Thanks and best regards,
Archimedes