Re: [gentoo-user] kswapd0 100% CPU with swapoff and no memory demands on system

[chin chong <fortalkingwith@gmail.com>]

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On Sat, May 3, 2014 at 10:16 AM, Chris Stankevitz <chrisstankevitz@gmail.com
> wrote:

> Hello,
>
> I have a small system:
>
> - 6GB drive
>
> - ext4 partition mounted readonly
>
> - swap partition that is not listed in fstab and not enabled.  (I will
> swapon it every few weeks or so if I need it for a large compile job)
>
> - 2 GB RAM
>
> When the system boots it processing video from a USB camera.  The
> program dynamically allocates and releases memory while it runs, but
> stores no data in memory or on disk (read-only).  The memory usage
> does not grow over time.
>
> When things are going well, top looks like so:
>
> ===
>
> Tasks:  68 total,   1 running,  67 sleeping,   0 stopped,   0 zombie
> %Cpu0  : 88.3 us, 11.7 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,
> 0.0 st
> %Cpu1  : 25.5 us,  2.3 sy,  0.0 ni, 72.1 id,  0.0 wa,  0.0 hi,  0.0 si,
> 0.0 st
> %Cpu2  :  6.0 us,  0.7 sy,  0.0 ni, 93.3 id,  0.0 wa,  0.0 hi,  0.0 si,
> 0.0 st
> %Cpu3  : 25.7 us,  2.3 sy,  0.0 ni, 72.0 id,  0.0 wa,  0.0 hi,  0.0 si,
> 0.0 st
> KiB Mem:   1861644 total,   161648 used,  1699996 free,     6948 buffers
> KiB Swap:        0 total,        0 used,        0 free,    57728 cached
>
>   PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
>  2129 root      20   0 1774440  81712  25388 S 160.0  4.4  25:55.46 obt
>   705 root      20   0       0      0      0 S   1.0  0.0   0:07.87 kswapd0
>  2049 ueyed     20   0  620472  14092  13652 S   1.0  0.8   0:09.34
> ueyeusbd
>
>
> ====
>
>
> Q1: Why does the kswapd0 process from time to time take up 100% CPU?
>
> Q2: Why does top show "cached swap" eventhough I do not have swap mounted?
>
> Q3: Is there anything I can do to prevent kswapd0 from using CPU on my
> system?  e.g. disable SWAP in the kernel config
>
> I suspect the answer to Q1 is:
>
> a) kernel is not configured properly for my hardware
>  or
> b) there is some bad side effect to my readonly root fs
>
> Thank you,
>
> Chris
>
>

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