From 3cb1215f1932bbde891be76d899b5b4fdec1c439 Mon Sep 17 00:00:00 2001 From: Artom Lifshitz Date: Wed, 2 Dec 2020 11:30:20 -0500 Subject: [PATCH] Docs: correct cpu_thread_policy explanation With the landing of the cpu-resources series in train [1], the hw:cpu_thread_policy extra spec has a different effect than before. Correct our documentation. [1] https://review.opendev.org/q/topic:bp/cpu-resources Change-Id: I338408b01b1d2328035dd92d2588710a20aba323 --- doc/source/user/flavors.rst | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/doc/source/user/flavors.rst b/doc/source/user/flavors.rst index 0b59da7f3f99..7fcbe1e745ec 100644 --- a/doc/source/user/flavors.rst +++ b/doc/source/user/flavors.rst @@ -475,16 +475,13 @@ CPU pinning policy - ``prefer``: (default) The host may or may not have an SMT architecture. Where an SMT architecture is present, thread siblings are preferred. - ``isolate``: The host must not have an SMT architecture or must emulate a - non-SMT architecture. If the host does not have an SMT architecture, each - vCPU is placed on a different core as expected. If the host does have an - SMT architecture - that is, one or more cores have thread siblings - then - each vCPU is placed on a different physical core. No vCPUs from other - guests are placed on the same core. All but one thread sibling on each - utilized core is therefore guaranteed to be unusable. - - ``require``: The host must have an SMT architecture. Each vCPU is allocated - on thread siblings. If the host does not have an SMT architecture, then it - is not used. If the host has an SMT architecture, but not enough cores with - free thread siblings are available, then scheduling fails. + non-SMT architecture. Hosts that support SMT (by reporting the + ``HW_CPU_HYPERTHREADING`` trait) are excluded. + - ``require``: The host must have an SMT architecture and must report the + ``HW_CPU_HYPERTHREADING`` trait. Each vCPU is allocated on thread siblings. + If the host does not have an SMT architecture, then it is not used. If the + host has an SMT architecture, but not enough cores with free thread + siblings are available, then scheduling fails. .. note::