Re: High vm scan rate and dropped keystrokes thru X?

[Paul Ripke <stix%stix.id.au@localhost>]

On Mon, Jul 26, 2021 at 11:56:13PM +0900, Izumi Tsutsui wrote:
> > NetBSD 9.2, amd64, 16GiB RAM, quad core + hyperthreading.
> > 
> > I've repeatedly noticed an issue where a large amount of disk reads can
> > result in lost keystrokes, jerky mouse behaviour and other weirdness.
>  :
> > "vmstat 1" during these events shows climbing runqueue, falling free
> > memory, high reclaim rate, very high scan rate, and 8 CPUs worth of
> > system time - and I hear the BIOS spinning up the CPU fan.
> 
> What "vmstat -m" shows?
> 
> if kmem-160 (or kmem-192) has a large number, maybe caused by
> radeondrmkms(4) leaks.
>  https://mail-index.netbsd.org/netbsd-bugs/2021/07/12/msg072460.html

No, no radeon here. To be clear, I don't believe this is a leak. It's
just some intermittently poor behaviour during high cache churn.

ksh$ vmstat -m | sort -k 8nr | head
vcachepl     336 61562054    0 60809350 2819365 2720482 98883 258691 0  inf    0
buf2k       2048  2710812    0  2543840 1224274 1136951 87323 116413 1    1    0
ffsdino2     256 60933737    0 60181639 1907605 1823135 84470 193820 0  inf    0
ffsino       256 60879348    0 60127246 1906802 1823012 83790 193820 0  inf    0
anonpl        32 38306110    0 35856325 43412  3062 40350 42502     0   inf    0
ncache       192 12485490    0 11813042 39948   122 39826 39828     0   inf    0
mutex         64 59812492    0 58941710 200286 164419 35867 51528   0   inf    0
bufpl        296  2450252    0  2210437 136128 114245 21883 24008   0   inf  381
buf16k      16384 1046417    0   983052 143815 126570 17245 22064   1     1    0
kmem-2048   2048   186643    2   169723 35112 26265  8847 12270     0   inf    1

'systat vm' shows the system mostly stalled with high sys CPU%, doing
page scans:

   18 users    Load  6.98  3.39  2.35                  Tue Jul 27 09:21:44

Proc:r  d  s        Csw  Traps SysCal  Intr   Soft  Fault     PAGING   SWAPPING
    18  1230       1215     58   4060   978    953     58     in  out   in  out
                                                        ops  
  82.7% Sy   0.5% Us   0.0% Ni   4.4% In  12.4% Id    pages
|    |    |    |    |    |    |    |    |    |    |
=========================================>%%                              forks
                                                                          fkppw
Anon      8904872  54%   zero     8928      1362 Interrupts               fksvm
Exec       457148   2%   wired  450292       284 TLB shootdown            pwait
File      3286872  20%   inact 2338880       100 cpu0 timer               relck
Meta      1371982    %   bufs   234364         4 ioapic0 pin 18           rlkok
 (kB)        real   swaponly      free       906 ioapic0 pin 16           noram
Active    9859004    1745392     10128           ioapic0 pin 23         3 ndcpy
Namei         Sys-cache     Proc-cache        68 msi1 vec 0             1 fltcp
    Calls     hits    %     hits     %                                 22 zfod
      236      234   99                                                   cow
                                                                     2048 fmin
  Disks:   seeks   xfers   bytes   %busy                             2730 ftarg
     wd0              20    253K    14.3                                  itarg
     wd1              18    242K    13.1                                  flnan
     cd0                                                               29 pdfre
     cd1                                                          1180584 pdscn
     sd0               1     91K     0.2
   raid0              21    273K    33.4


-- 
Paul Ripke
"Great minds discuss ideas, average minds discuss events, small minds
 discuss people."
-- Disputed: Often attributed to Eleanor Roosevelt. 1948.