[issue2118] swap filled on machine with heavy activity+swapcache,

New submission from Francois Tigeot <[e-mail]>:

pkgbox64.dragonflybsd.org uses 64GB swapcache + 8GB RAM

When under heavy load (Opengrok indexing, Hammer daily cleanup and bulk build
running at the same time), its swap filled entirely

This kernel message was logged on the console:
  swap_pager_getswapspace: failed

And the system behaved erratically:
  dmesg: sysctl kern.msgbuf: Cannot allocate memory

Killing processes had no lasting effect; as soon as a little bit of swap
emptied, it was filled again.

Even though swap was 99% filled and vm.swapcache.maxswappct much lower, the
kernel still tried to add data to swap.
Reducing vm.swapcache.maxswappct further (40%, 20%, etc...) had no effect.

The only way to force swap to drain was to set vm.swapcache.maxswappct to 0

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assignedto: dillon
keyword: kernel
messages: 10051
nosy: dillon, ftigeot
priority: critical
status: unread
title: swap filled on machine with heavy activity+swapcache, swap doesn't drain

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<http://bugs.dragonflybsd.org/issue2118>
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