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=3D216759 --- 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-P= M 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 hyperv= isor except for programmed by VMWare loophole is penalised (don't know though wh= ich 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 sti= ll BSD does not check that in any case in its TSC code (or I might be misreadi= ng 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 !=3D VM_GUEST_= KVM)) return (-100); --=20 You are receiving this mail because: You are the assignee for the bug.=
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