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Subject: [Bug 216759] [kern] Memory speed with small blocks (1K) up to 35
 times slower than host system (under QEMU emulation, but not only)
Date: Tue, 28 Feb 2017 15:55:16 +0000
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D216759

--- Comment #10 from andrew@azar-a.net ---
About linux, seems kvm-clock is broken somehow, I adjusted to TSC and got 3=
700
of the host...


And it seems same is for FreeBSD. Only BSD forces HPET or ACPI on any
virtualised platform. So there is only manual way to force to TSC-low which
brings us back to 3700

Seems like kernel timecounters code has been written in times of just appea=
ring
invariant_tsc and it does not know anything about CPU flags constant_tsc
nonstop_tsc tsc_deadline_timer etc...

It's really simple in code. If it's invariant or SMP it's boosted... and th=
at's
it:

https://github.com/freebsd/freebsd/blob/21c11d113415f2c87107b6735407b147fae=
0b851/sys/x86/x86/tsc.c

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