Date: Tue, 21 Mar 2017 19:04:40 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-virtualization@FreeBSD.org Subject: [Bug 216759] [kern] Memory speed with small blocks (1K) up to 35 times slower than host system (under QEMU emulation, but not only) Message-ID: <bug-216759-27103-LBBbjgQASa@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-216759-27103@https.bugs.freebsd.org/bugzilla/> References: <bug-216759-27103@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=216759 --- Comment #17 from andrew@azar-a.net --- (In reply to deJong from comment #16) It doesn't seem like the patchset is applied at all. > kern.timecounter.choice: TSC-low(-100) i8254(0) ACPI-fast(900) HPET(950) dummy(-1000000) It should add kvmclock to that list which is obviously not there. Forcing TSC-low on KVM VM when the host trusts it more than HPET and ACPI-PM is foolproof imo. It's obvious that the choice for this has been designed a long time ago and has been programmed this way because back then TSC really sucked and any hypervisor except for programmed by VMWare loophole is penalised (don't know though which because xen requires more workarounds in the kernel and I don't really know how bhyve runs it).. So obviously this part of code should be reworked if ((!smp_tsc && !tsc_is_invariant) || vm_guest) return (-100); X86_FEATURE_CONSTANT_TSC is not checked at all (this is from linux, but still BSD does not check that in any case in its TSC code (or I might be misreading the magic tsc_is_invariant variable)). And most of all the vm_guest check should go away. It's a terrible hack nowadays as this bug shows. I did not try this yet but maybe something like this will help if ((!smp_tsc && !tsc_is_invariant) || (vm_guest && vm_guest != VM_GUEST_KVM)) return (-100); -- You are receiving this mail because: You are the assignee for the bug.
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