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[Qemu-devel] [PULL v4 17/43] numa: deprecate 'mem' parameter of '-numa n
From: |
Eduardo Habkost |
Subject: |
[Qemu-devel] [PULL v4 17/43] numa: deprecate 'mem' parameter of '-numa node' option |
Date: |
Wed, 3 Jul 2019 15:07:00 -0300 |
From: Igor Mammedov <address@hidden>
The parameter allows to configure fake NUMA topology where guest
VM simulates NUMA topology but not actually getting performance
benefits from it. The same or better results could be achieved
using 'memdev' parameter.
Beside of unpredictable performance, '-numa node.mem' option has
other issues when it's used with combination of -mem-path +
+ -mem-prealloc + memdev backends (pc-dimm), breaking binding of
memdev backends since mem-path/mem-prealloc are global and affect
the most of RAM allocations.
It's possible to make memdevs and global -mem-path/mem-prealloc
to play nicely together but that will just complicate already
complicated code and add unobious ways it could break on 2
different memmory allocation pathes and their combinations.
Instead of it, consolidate all guest RAM allocation over memdev
which still allows to create fake NUMA configurations if desired
and leaves one simplifyed code path to consider when it comes
to guest RAM allocation.
To achieve desired simplification deprecate 'mem' parameter as its
ad-hoc partitioning of initial RAM MemoryRegion can't be translated
to memdev based backend transparently to users and in compatible
manner (migration wise).
Later down the road that will allow to consolidate means of how
guest RAM is allocated and would permit us to clean up quite
a bit memory allocations and numa code, leaving only 'memdev'
implementation in place.
Signed-off-by: Igor Mammedov <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Eduardo Habkost <address@hidden>
---
numa.c | 2 ++
qemu-deprecated.texi | 16 ++++++++++++++++
2 files changed, 18 insertions(+)
diff --git a/numa.c b/numa.c
index 7594eb5a7e..7d449c7e95 100644
--- a/numa.c
+++ b/numa.c
@@ -122,6 +122,8 @@ static void parse_numa_node(MachineState *ms,
NumaNodeOptions *node,
if (node->has_mem) {
numa_info[nodenr].node_mem = node->mem;
+ warn_report("Parameter -numa node,mem is deprecated,"
+ " use -numa node,memdev instead");
}
if (node->has_memdev) {
Object *o;
diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
index df04f2840b..44c9a95966 100644
--- a/qemu-deprecated.texi
+++ b/qemu-deprecated.texi
@@ -88,6 +88,22 @@ The @code{-realtime mlock=on|off} argument has been replaced
by the
The ``-virtfs_synth'' argument is now deprecated. Please use ``-fsdev synth''
and ``-device virtio-9p-...'' instead.
+@subsection -numa node,mem=@var{size} (since 4.1)
+
+The parameter @option{mem} of @option{-numa node} is used to assign a part of
+guest RAM to a NUMA node. But when using it, it's impossible to manage
specified
+RAM chunk on the host side (like bind it to a host node, setting bind policy,
...),
+so guest end-ups with the fake NUMA configuration with suboptiomal performance.
+However since 2014 there is an alternative way to assign RAM to a NUMA node
+using parameter @option{memdev}, which does the same as @option{mem} and adds
+means to actualy manage node RAM on the host side. Use parameter
@option{memdev}
+with @var{memory-backend-ram} backend as an replacement for parameter
@option{mem}
+to achieve the same fake NUMA effect or a properly configured
+@var{memory-backend-file} backend to actually benefit from NUMA configuration.
+In future new machine versions will not accept the option but it will still
+work with old machine types. User can check QAPI schema to see if the legacy
+option is supported by looking at MachineInfo::numa-mem-supported property.
+
@section QEMU Machine Protocol (QMP) commands
@subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)
--
2.18.0.rc1.1.g3f1ff2140
- [Qemu-devel] [PULL v4 07/43] hw/i386: Replace global smp variables with machine smp properties, (continued)
- [Qemu-devel] [PULL v4 07/43] hw/i386: Replace global smp variables with machine smp properties, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 08/43] hw/arm: Replace global smp variables with machine smp properties, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 10/43] vl.c: Replace smp global variables with smp machine properties, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 09/43] hw: Replace global smp variables with MachineState for all remaining archs, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 11/43] i386: Add die-level cpu topology to x86CPU on PCMachine, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 12/43] hw/i386: Adjust nr_dies with configured smp_dies for PCMachine, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 15/43] pc: fix possible NULL pointer dereference in pc_machine_get_device_memory_region_size(), Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 13/43] i386/cpu: Consolidate die-id validity in smp context, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 14/43] i386: Update new x86_apicid parsing rules with die_offset support, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 16/43] machine: show if CLI option '-numa node, mem' is supported in QAPI schema, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 17/43] numa: deprecate 'mem' parameter of '-numa node' option,
Eduardo Habkost <=
- [Qemu-devel] [PULL v4 19/43] hppa: Delete unused hppa_cpu_list() function, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 21/43] deprecate -mem-path fallback to anonymous RAM, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 22/43] i386: Don't print warning if phys-bits was set automatically, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 18/43] numa: deprecate implict memory distribution between nodes, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 20/43] target/i386: fix feature check in hyperv-stub.c, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 25/43] x86/cpu: use FeatureWordArray to define filtered_features, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 24/43] i386: make 'hv-spinlocks' a regular uint32 property, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 31/43] i386: Introduce SnowRidge CPU model, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 23/43] i386: Fix signedness of hyperv_spinlock_attempts, Eduardo Habkost, 2019/07/03
- [Qemu-devel] [PULL v4 32/43] qmp: Add "alias-of" field to query-cpu-definitions, Eduardo Habkost, 2019/07/03