K 10
svn:author
V 3
mav
K 8
svn:date
V 27
2021-03-15T03:04:05.071623Z
K 7
svn:log
V 799
Save context switch per I/O for iSCSI and IOCTL frontends.

Introduce new CTL core KPI ctl_run(), preprocessing I/Os in the caller
context instead of scheduling another thread just for that.  This call
may sleep, that is not acceptable for some frontends like the original
CAM/FC one, but iSCSI already has separate sleepable per-connection RX
threads, and another thread scheduling is mostly just a waste of time.
IOCTL frontend actually waits for the I/O completion in the caller
thread, so the use of another thread for this has even less sense.

With this change I can measure ~5% IOPS improvement on 4KB iSCSI I/Os
to ZFS.

MFC after:	1 month

(cherry picked from commit 812c9f48a2b7bccc31b2a6077b299822357832e4)

Git Hash:   cfd358d99732463a9ec2ed3d81374dae9f12b112
Git Author: mav@FreeBSD.org
END