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kern/subr_trap.c: repair the HPTS performance hack in userret()

Description

kern/subr_trap.c: repair the HPTS performance hack in userret()

It wasn't functional as subr_trap.c doesn't include opt_inet.h. Put a
better comment provided by gallatin@ in place of the old one. The idea
is to use userret() as a cheap place to call a soft clock. This approach
saves CPU on busy machines and saves power on idle machines.
An alternative would be to constantly schedule callouts. Running with
neither callouts nor the soft clock ruins HPTS precision.

Reviewed by: tuexen, rrs
Differential Revision: https://reviews.freebsd.org/D42860

(cherry picked from commit e3cbc572f1541fdc18be9971d23e210d5018e662)

Details

Provenance
glebiusAuthored on Dec 4 2023, 6:19 PM
Reviewer
tuexen
Differential Revision
D42860: kern/subr_trap.c: repair the HPTS performance hack in userret()
Parents
rG2707135d0959: hpts/lro: make tcp_lro_flush_tcphpts() and tcp_run_hpts() pointers
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