b5e6091885
spa_thread() and the "System Duty Cycle" scheduling class are from
Illumos and have not yet been adapted to Linux or FreeBSD.
HAVE_SPA_THREAD has long been explicitly undefined and used to mark
spa_thread(), but there's some related taskq code that can never be
invoked without it, which makes some already-tricky code harder to read.
HAVE_SYSDC is introduced in this commit to mark the SDC parts. SDC
requires spa_thread(), but the inverse is not true, so they are
separate.
I don't want to make the call to just remove it because I still harbour
hopes that OpenZFS could become a first-class citizen on Illumos
someday. But hopefully this will at least make the reason it exists a
bit clearer for people without long memories and/or an interest in
history.
For those that are interested in the history, the original FreeBSD port
of ZFS (before ZFS-on-Linux was adopted there) did have a spa_thread(),
but not SDC. The last version of that before it was removed can be read
here:
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| .. | ||
| avl | ||
| icp | ||
| lua | ||
| nvpair | ||
| os | ||
| unicode | ||
| zcommon | ||
| zfs | ||
| zstd | ||
| .gitignore | ||
| Kbuild.in | ||
| Makefile.bsd | ||
| Makefile.in | ||