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qemu-options.hx: Improve formatting in colo-compare docs

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The colo-compare option documentation has some formatting issues: it
uses a "@var{...}" syntax which is not used elsewhere and which is
rendered literally into the HTML documentation.  The bare "@" sign
also results in an unintended 'mailto:' hyperlink.

Rewrite this into the style we seem to use most in the rest of
the command line options, where an option which takes an argument
is written as "my-option=<thing>".

We take the opportunity to make the documentation a little clearer
by splitting up the long paragraph and using preformatted-text
markup for the names of the suboptions.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Zhang Chen <zhangckid@gmail.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20260115142629.665319-5-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell
2026-01-15 14:26:29 +00:00
parent b755c5e7ec
commit 62580edc02
1 changed files with 25 additions and 16 deletions
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41
qemu-options.hx
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@@ -5972,22 +5972,31 @@ SRST
stored. The file format is libpcap, so it can be analyzed with
tools such as tcpdump or Wireshark.
``-object colo-compare,id=id,primary_in=chardevid,secondary_in=chardevid,outdev=chardevid,iothread=id[,vnet_hdr_support][,notify_dev=id][,compare_timeout=@var{ms}][,expired_scan_cycle=@var{ms}][,max_queue_size=@var{size}]``
Colo-compare gets packet from primary\_in chardevid and
secondary\_in, then compare whether the payload of primary packet
and secondary packet are the same. If same, it will output
primary packet to out\_dev, else it will notify COLO-framework to do
checkpoint and send primary packet to out\_dev. In order to
improve efficiency, we need to put the task of comparison in
another iothread. If it has the vnet\_hdr\_support flag,
colo compare will send/recv packet with vnet\_hdr\_len.
The compare\_timeout=@var{ms} determines the maximum time of the
colo-compare hold the packet. The expired\_scan\_cycle=@var{ms}
is to set the period of scanning expired primary node network packets.
The max\_queue\_size=@var{size} is to set the max compare queue
size depend on user environment.
If user want to use Xen COLO, need to add the notify\_dev to
notify Xen colo-frame to do checkpoint.
``-object colo-compare,id=<id>,primary_in=<chardevid>,secondary_in=<chardevid>,outdev=<chardevid>,iothread=<id>[,vnet_hdr_support][,notify_dev=<id>][,compare_timeout=<time_ms>][,expired_scan_cycle=<time_ms>][,max_queue_size=<maxsize>]``
Colo-compare gets packets from the chardev backends specified by
``primary_in`` and ``secondary_in``, and compares whether the payloads
of the primary packet and the secondary packet are the same.
If they match, it will output the primary packet to the chardev
backend specified by ``outdev``; otherwise it will notify COLO-framework
to do a checkpoint and send the primary packet to ``outdev``.
In order to improve efficiency, we need to put the task of comparison in
another iothread; the ``iothread`` option specifies that iothread object
(which your commandline should create).
The ``vnet_hdr_support`` flag tells
colo compare to pass the vnet header length when it sends and receives packets.
The ``compare_timeout`` option sets the maximum time that
colo-compare will hold the packet for, in ms.
The ``expired_scan_cycle`` option sets the period of scanning expired
primary node network packets, in ms.
The ``max_queue_size`` option sets the max compare queue size.
If you want to use Xen COLO, you need to specify ``notify_dev`` to
tell colo-compare how to notify Xen colo-frame to do a checkpoint.
COLO-compare must be used with the help of filter-mirror,
filter-redirector and filter-rewriter.