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List:       gentoo-user
Subject:    Re: [gentoo-user] Getting output of a program running in background after a crash
From:       Frank Steinmetzger <Warp_7 () gmx ! de>
Date:       2023-10-09 11:09:10
Message-ID: ZSPfVnPaYDRDfdfd () kern
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Am Sun, Oct 08, 2023 at 07:44:06PM -0500 schrieb Dale:

> Just as a update.   The file system I was trying to do a file system
> check on was my large one, about 40TBs worth.   While running the file
> system check, it started using HUGE amounts of memory.   It used almost
> all my 32GBs and most of swap as well.   It couldn't finish due to not
> enough memory, it literally crashed itself.   So, I don't know if this is
> because of some huge problem or what but if this is expected behavior,
> don't try to do a file system check on devices that large unless you
> have a LOT of memory.  

Or use a different filesystem. O:-)

> I ended up recreating the LVM devices from scratch and redoing the
> encryption as well.   I have backups tho.   This all started when using
> pvmove to replace a hard drive with a larger drive.   I guess pvmove
> isn't always safe.

I think that may be a far-fetched conclusion. If it weren't safe, it 
wouldn't be in the software – or at least not advertised as safe.

> P. S.   I currently have my backup system on my old Gigabyte 770T mobo
> and friends.   It is still a bit slower than copying when no encryption
> is used so I guess encryption does slow things down a bit.   That said,
> the CPU does hang around 50% most of the time.   htop doesn't show what
> is using that so it must be IO or encryption.

You can add more widgets ("meters") to htop, one of them shows disk 
throughput. But there is none for I/O wait. One tool that does show that is 
glances. And also dstat which I mentioned a few days ago. Not only can dstat 
tell you the total percentage, but also which process is the most expensive 
one.

I set up bash aliases for different use cases of dstat:
alias ,d='dstat --time --cpu --disk -D $(ls /dev/sd? /dev/nvme?n? /dev/mmcblk? \
2>/dev/null | tr "\n" ,) --net --mem --swap' alias ,dd='dstat --time --cpu --disk \
--disk-util -D $(ls /dev/sd? /dev/nvme?n? /dev/mmcblk? 2>/dev/null | tr "\n" ,) \
--mem-adv' alias ,dm='dstat --time --cpu --disk -D $(ls /dev/sd? /dev/nvme?n? \
/dev/mmcblk? 2>/dev/null | tr "\n" ,) --net --mem-adv --swap' alias ,dt='dstat --time \
--cpu --disk -D $(ls /dev/sd? /dev/nvme?n? /dev/mmcblk? 2>/dev/null | tr "\n" ,) \
--net --mem --swap --top-cpu --top-bio --top-io --top-mem'

Because I attach external storage once in a while, I use a dynamic list of 
devices to watch that is passed to the -D argument. If I don't use -D, dstat 
will only show a total for all drives.

The first is a simple overview (d = dstat).

The second is the same but only for disk statistics (dd = dstat disks). I 
use it mostly on my NAS (five SATA drives in total, which creates a very 
wide table).

The third shows more memory details like dirty cache (dm = dstat memory), 
which is interesting when copying large files.

And the last one shows the top "pigs", i.e. expensive processes in terms of 
CPU, IO and memory (dt = dstat top).

> Or something kernel
> related that htop doesn't show.   No idea.  

Perhaps my tool tips give you ideas. :)

-- 
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