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From b733703cfcc4b4e8966051ba20bed301645331d0 Mon Sep 17 00:00:00 2001
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Message-Id: <b733703cfcc4b4e8966051ba20bed301645331d0@dist-git>
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From: Michal Privoznik <mprivozn@redhat.com>
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Date: Thu, 18 Apr 2019 18:58:58 +0200
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Subject: [PATCH] qemu: Set up EMULATOR thread and cpuset.mems before
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exec()-ing qemu
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https://bugzilla.redhat.com/show_bug.cgi?id=1695434
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It's funny how this went unnoticed for such a long time. Long
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story short, if a domain is configured with
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VIR_DOMAIN_NUMATUNE_MEM_STRICT libvirt doesn't really honour
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that. This is because of 7e72ac787848 after which libvirt allowed
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qemu to allocate memory just anywhere and only after that it used
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some magic involving cpuset.memory_migrate and cpuset.mems to
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move the memory to desired NUMA nodes. This was done in order to
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work around some KVM bug where KVM would fail if there wasn't a
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DMA zone available on the NUMA node. Well, while the work around
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might stopped libvirt tickling the KVM bug it also caused a bug
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on libvirt side: if there is not enough memory on configured NUMA
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node(s) then any attempt to start a domain must fail. Because of
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the way we play with guest memory domains can start just happily.
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The solution is to move the child we've just forked into emulator
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cgroup, set up cpuset.mems and exec() qemu only after that.
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This basically reverts 7e72ac787848b7434c9 which was a workaround
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for kernel bug. This bug was apparently fixed because I've tested
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this successfully with recent kernel.
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Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
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Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
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(cherry picked from commit 0eaa4716e1b8f6eb59d77049aed3735c3b5fbdd6)
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Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
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Message-Id: <efd9d64c94a027281c244c05f69cc9f4c31ed83b.1555606711.git.mprivozn@redhat.com>
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Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
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---
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src/qemu/qemu_process.c | 8 ++++----
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1 file changed, 4 insertions(+), 4 deletions(-)
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diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
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index 7d04a6e226..208c64381c 100644
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--- a/src/qemu/qemu_process.c
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+++ b/src/qemu/qemu_process.c
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@@ -6432,6 +6432,10 @@ qemuProcessLaunch(virConnectPtr conn,
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if (qemuProcessInitCpuAffinity(vm) < 0)
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goto cleanup;
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+ VIR_DEBUG("Setting emulator tuning/settings");
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+ if (qemuProcessSetupEmulator(vm) < 0)
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+ goto cleanup;
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+
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VIR_DEBUG("Setting cgroup for external devices (if required)");
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if (qemuSetupCgroupForExtDevices(vm, driver) < 0)
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goto cleanup;
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@@ -6523,10 +6527,6 @@ qemuProcessLaunch(virConnectPtr conn,
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if (qemuProcessDetectIOThreadPIDs(driver, vm, asyncJob) < 0)
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goto cleanup;
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- VIR_DEBUG("Setting emulator tuning/settings");
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- if (qemuProcessSetupEmulator(vm) < 0)
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- goto cleanup;
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-
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VIR_DEBUG("Setting global CPU cgroup (if required)");
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if (qemuSetupGlobalCpuCgroup(vm) < 0)
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goto cleanup;
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--
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2.21.0
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