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qemu-options.hx: Update descriptions of memory options for NUMA node 

This commit adds the following description:
1. `memdev` option is recommended over `mem` option (see [1,2])
2. users must specify memory for all NUMA nodes (see [2])

This commit also separates descriptions for `mem` and `memdev` into two
paragraphs. The old doc describes legacy `mem` option first, and it was
a bit confusing.

Related documentation:
[1] https://wiki.qemu.org/ChangeLog/5.1#Incompatible_changes
[2] https://www.qemu.org/docs/master/about/removed-features.html

Signed-off-by: Yohei Kojima <y-koj@outlook.jp>
Message-Id: <TYZPR06MB5418D6B0175A49E8E76988439D8E9@TYZPR06MB5418.apcprd06.prod.outlook.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
[AJB: fix documentation in commit message]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230424092249.58552-15-alex.bennee@linaro.org>
This commit is contained in:
Yohei Kojima 2023-04-24 10:22:45 +01:00 committed by Alex Bennée
parent d044b7c33a
commit 4f513984ed
1 changed files with 14 additions and 7 deletions
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21
qemu-options.hx
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@ -405,15 +405,22 @@ SRST
-numa node,nodeid=0 -numa node,nodeid=1 \
-numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1
Legacy '\ ``mem``\ ' assigns a given RAM amount to a node (not supported
for 5.1 and newer machine types). '\ ``memdev``\ ' assigns RAM from
a given memory backend device to a node. If '\ ``mem``\ ' and
'\ ``memdev``\ ' are omitted in all nodes, RAM is split equally between them.
'\ ``memdev``\ ' option assigns RAM from a given memory backend
device to a node. It is recommended to use '\ ``memdev``\ ' option
over legacy '\ ``mem``\ ' option. This is because '\ ``memdev``\ '
option provides better performance and more control over the
backend's RAM (e.g. '\ ``prealloc``\ ' parameter of
'\ ``-memory-backend-ram``\ ' allows memory preallocation).
For compatibility reasons, legacy '\ ``mem``\ ' option is
supported in 5.0 and older machine types. Note that '\ ``mem``\ '
and '\ ``memdev``\ ' are mutually exclusive. If one node uses
'\ ``memdev``\ ', the rest nodes have to use '\ ``memdev``\ '
option, and vice versa.
'\ ``mem``\ ' and '\ ``memdev``\ ' are mutually exclusive.
Furthermore, if one node uses '\ ``memdev``\ ', all of them have to
use it.
Users must specify memory for all NUMA nodes by '\ ``memdev``\ '
(or legacy '\ ``mem``\ ' if available). In QEMU 5.2, the support
for '\ ``-numa node``\ ' without memory specified was removed.
'\ ``initiator``\ ' is an additional option that points to an
initiator NUMA node that has best performance (the lowest latency or