[Bug 256217] [tcp] High system load because of interrupts with RACK

From: <bugzilla-noreply_at_freebsd.org>
Date: Fri, 28 May 2021 10:57:00 UTC

            Bug ID: 256217
           Summary: [tcp] High system load because of interrupts with RACK
           Product: Base System
           Version: 13.0-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: chris@cretaforce.gr

After I enable RACK I notice high system load because of high interrupts.

I compile a kernel with these options:

makeoptions   WITH_EXTRA_TCP_STACKS=1
options       TCPHPTS
options       RATELIMIT

I add in the /etc/sysctl.conf :


and in /boot/loader.conf :


After I reboot the servers I notice 5% - 45% interrupts (some servers show more
and some less) using "top".

The issue happens with "kern.eventtimer.timer=LAPIC" too.

Then I disable RACK and switch back to LAPIC and after reboot "top" shows 0.0%
- 0.1% interrupts.

Switching to "net.inet.tcp.functions_default=freebsd" without reboot the
interrupts don't decrease.

Searching for similar issues I found this:

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