[mythtv-users] MythFrontend out of memory problem
Jay Foster
jayf0ster at roadrunner.com
Thu May 19 17:17:53 UTC 2022
On 5/19/2022 10:03 AM, Kenneth Emerson wrote:
>
>
> On Mon, Apr 11, 2022, 2:53 PM Kenneth Emerson
> <kenneth.emerson at gmail.com> wrote:
>
>
>
> On Mon, Apr 11, 2022, 1:04 PM Kenneth Emerson
> <kenneth.emerson at gmail.com> wrote:
>
>
>
> On Mon, Apr 11, 2022, 12:53 AM Stephen Worthington
> <stephen_agent at jsw.gen.nz> wrote:
>
> On Sun, 10 Apr 2022 23:00:17 -0500, you wrote:
>
>
> >> Stephen:
> >
> >
> >
> >The system RAM is 8Gb. There is a 2Gb swap space. There
> are about 3,000
> >recordings. Here is the output from swap.sh:
> >
> >
> >ken at mythtv:~$ ./swap.sh
> >
> >
> >..............................
> >
> >Overall swap used: 798096 kB
> >
> >
> >========================================
> >
> >kB pid name
> >
> >
> >========================================
> >
> >404072 1408 mythfrontend.re <http://mythfrontend.re>
> >
> >77376 1365 xfdesktop
> >
> >42080 1277 xfwm4
> >
> >38504 1377 applet.py
> >
> >37120 1509 blueman-tray
> >
> >34504 1426 blueman-applet
> >
> >15624 1131 xfce4-session
> >
> >14224 1310 panel-1-whisker
> >
> >12480 1321 panel-10-pulsea
> >
> >12224 1317 panel-8-statusn
> >
> >11536 1314 panel-6-notific
> >
> >10552 1401 update-notifier
> >
> >10216 1411 nm-applet
> >
> >9408 1360 Thunar
> >
> >9336 1282 xfsettingsd
> >
> >8608 1313 panel-5-systray
> >
> >8576 1318 panel-9-power-m
> >
> >8528 1385 xfce4-power-man
> >
> >8240 1315 panel-7-indicat
> >
> >5840 1283 xfce4-panel
> >
> >3280 12076 bash
> >
> >3272 1382 xiccd
> >
> >3032 3791 bash
> >
> >2688 1123 systemd
> >
> >2640 1442 polkit-gnome-au
> >
> >1920 1130 pulseaudio
> >
> >1224 1437 agent
> >
> >504 1145 dbus-daemon
> >
> >248 3784 tmux: server
> >
> >240 1368 mythfrontend
> >
> >
> >ken at mythtv:~$ free -m
> >
> >
> > total used free
> shared buff/cache
> >available
> >Mem: 7934 2964 202 7 4768
> > 4668
> >
> >If it's meaningful the CPU is an Intel i5-2500K 3.3GHz
> >
> >Perhaps I am hitting some limit on number of recordings,
> but I don't ever
> >remember there being a (soft?) limit.
> >The system is a bit old, but I would hope it's powerful
> enough. I only use
> >it as a media center with only MythTv as the main
> application.
> >
> >Regards,
> >
> >Ken Emerson
>
> With 8 Gibytes of RAM, it should be fine. Only 3000
> recordings is not
> a problem (I have 52880 on an 8 Gibyte frontend/backend
> system). There
> is no fixed limit on recordings - the list can grow as big
> as your
> system will allow, although things do slow down a bit when
> you have as
> many as I do.
>
> It does look like the swap space is filling up though - I
> would
> suggest increasing that to 8 Gibytes. But it is currently
> using
> 798096 kiB, which is under half full so it is not obvious
> that it will
> run out of swap.
>
> I have my system and swap partitions on a fast M.2 NVME
> SSD, which
> helps with swapping.
>
> The free command gives you the total RAM and swap usage.
> This is my
> system with mythfrontend showing my recordings list:
>
> root at mypvr:~# free -m
> total used free shared buff/cache
> available
> Mem: 7902 2829 120 23 4952
> 4752
> Swap: 10239 1556 8683
>
> (Sorry about the line wrapping - my email client does that
> and it is
> not able to be turned off).
>
> So your frontend only system with only 3000 recordings
> should be just
> fine. So my best guess is that something is triggering a
> bug that is
> causing a memory leak. But the problem might be in
> another program,
> rather than mythfrontend. The OOM system is known for
> killing the
> largest RAM user, when the problem program that is
> suddenly using up
> RAM is a different program.
>
> There was one old bug that caused the cache directory not
> to be
> cleaned up properly, and mythfrontend would then load the
> cache and
> run out of RAM. That was fixed a while ago, but it is
> possible that
> you still somehow have a huge cache. So take a look at
> $(HOME)/.mythtv/cache and see how big it is:
>
> root at mypvr:~# du -hcs /home/stephen/.mythtv/cache/
> 376M /home/stephen/.mythtv/cache/
> 376M total
>
> This mine now, but when the bug was happening, it was many
> gibytes. If
> yours is too large, shut down mythfrontend and do:
>
> rm -r $(HOME)/.mythtv/cache
>
> Mythfrontend should then rebuild the cache as required.
>
> I would suggest upgrading to v32. That is the currently
> supported
> version, so if you have a problem that needs the devs to
> fix it, you
> will need to be on v32 for them to be interested. And it
> is vaguely
> possible your problem may be fixed already in v32-fixes.
>
>
> Stephen:
>
> Unfortunately, I decided to take the plunge and upgrade to 32.
> Looked simple; however, in stuck years ago right at the
> beginning running mythtv-setup with "Failed to get schema
> upgrade lock". Can't go back or forward at this point. I have
> a good DB backup just don't know what to do with it.
>
> Ken Emerson
>
>
> Update:
>
> I changed the hostname in the setup dialog from localhost to
> mythtv (the actual hostname) and then rebooted. The master backend
> ran after the reboot and asked me if I wanted to upgrade the
> schema; answered yes and all I good now; upgraded from 1361 to
> 1376. Don't fully understand the problem. There were no clues in
> the mythtv-setup log. Perhaps the backend takes care of all that now?
>
> Anyway, sorry for all the cruft.
>
> BTW: 681Mb in .mythtv/cache
> Will have to wait several weeks to see if the OOM kill problem is
> gone.
>
> Thanks for your time and help.
>
> Regards,
> Ken Emerson
>
>
> It's been a month now, and I haven't seen a re-occurance of the OOM
> killer taking out the frontend; however, by keeping an eye out on
> resources I notice that memory is still tight. I've updated myth to
> version 32 and did maintenance on the cache disk space as suggested.
> This morning when a OTA program was recording with no one watching any
> recordings, the frontend.real task (using top) was using the majority
> of resources, both cpu and memory. CPU was 47-80% range with memory
> 80-90% range. Along with the frontend, mythcommflag was also running
> using minimal resources as was the backend. frontend.real was always
> first in listing using top looking at both cpu and memory.
>
> Using free, there was only about 60mb memory available (system has 8
> gb installed). I don't understand what the frontend is doing when
> there is nothing being played back: just sitting at the recordings
> menu. I also have a 2gb swap partition that is also more than 90%
> consumed.
>
> FYI: This is a dedicated frontend/backend server with no other
> services running other than what myth requires.
>
> I've ordered and am now waiting for an additional 8gb of memory but
> would appreciate any enlightenment on what the frontend is busy doing.
>
> Regards,
>
> Ken Emerson
>
>
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My combined FE/BE also has 8GB or RAM and has no issues (running 0.28).
Something to keep in mind when looking at how much RAM is 'free'
(/proc/meminfo) is that the linux kernel will use any available RAM for
caching, so the reported free RAM is usually low. This is not indicative
of a problem (i.e., memory leak).
Jay
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