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To: scottl@samsco.org
From: "M. Warner Losh" <imp@bsdimp.com>
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Cc: src-committers@freebsd.org, jhb@freebsd.org, bde@zeta.org.au,
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Subject: Re: cvs commit: src/sys/amd64/amd64 cpu_switch.S machdep.c
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In message: <4357AAFE.2070002@samsco.org>
            Scott Long <scottl@samsco.org> writes:
: However, I'd like to revisit the HZ=1000 decision for 7-CURRENT.

At Timing Solutions, we run with HZ=1000 to reduce the latency for
interacting with serial devices (since we have highly synchronous
protocols that are spoken over them).  Other than that, we've seen no
performance differences between HZ=100 and HZ=1000 in other areas of
our systems.  We have noted a small increase in overhead with 1000,
but since we have plenty of CPU to burn, we burn a little to get
better latencies...  We'll likely tune the number based on our
experience, so changing the default HZ won't impact us.

Warner