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Konrad Rzeszutek Wilk
65a11256f2
Updating to make it clear that free_memory reported by 'xl info' is influenced by the outstanding claim value. That is the free memory that will be available to the host once all outstanding claims have been completed. This modifies the behavior that the patch titled "xl: 'xl info' print outstanding claims if enabled (claim_mode=1 in xl.conf)" had - which reported the outstanding claims and nothing else. The free_pages as reported by the hypervisor is the currently available count of pages on the heap. The outstanding pages is the total amount of pages reserved for guests (so not taken from the heap yet). As guests are being populated the memory from the heap shrinks and the outstanding count of pages decreases. The total memory used for guests increases. As the available count of pages on the heap and outstanding claims are intertwined, report the amount of free memory available to be a combination of that. That is free heap memory minus the outstanding pages. We also make some odd choices in reporting. By default we will only display 'outstanding_claims' if the claim_mode is enabled in the global configuration file. However, if there are outstanding claims, we will ignore the claim_mode and report these values. Suggested-by: Ian Jackson <Ian.Jackson@eu.citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
174 lines
4.6 KiB
Plaintext
174 lines
4.6 KiB
Plaintext
=head1 NAME
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/etc/xen/xl.conf - XL Global/Host Configuration
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=head1 DESCRIPTION
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The F<xl.conf> file allows configuration of hostwide C<xl> toolstack
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options.
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For details of per-domain configuration options please see
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L<xl.cfg(5)>.
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=head1 SYNTAX
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The config file consists of a series of C<KEY=VALUE> pairs.
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A value C<VALUE> is one of:
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=over 4
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=item B<"STRING">
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A string, surrounded by either single or double quotes.
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=item B<NUMBER>
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A number, in either decimal, octal (using a C<0> prefix) or
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hexadecimal (using an C<0x> prefix).
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=item B<BOOLEAN>
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A C<NUMBER> interpreted as C<False> (C<0>) or C<True> (any other
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value).
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=item B<[ VALUE, VALUE, ... ]>
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A list of C<VALUES> of the above types. Lists are homogeneous and are
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not nested.
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=back
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The semantics of each C<KEY> defines which form of C<VALUE> is required.
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=head1 OPTIONS
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=over 4
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=item B<autoballoon="off"|"on"|"auto">
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If set to "on" then C<xl> will automatically reduce the amount of
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memory assigned to domain 0 in order to free memory for new domains.
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If set to "off" then C<xl> will not automatically reduce the amount of
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domain 0 memory.
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If set to "auto" then auto-ballooning will be disabled if the
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C<dom0_mem> option was provided on the Xen command line.
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You are strongly recommended to set this to C<"off"> (or C<"auto">) if
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you use the C<dom0_mem> hypervisor command line to reduce the amount
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of memory given to domain 0 by default.
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Default: C<"auto">
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=item B<run_hotplug_scripts=BOOLEAN>
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If disabled hotplug scripts will be called from udev, as it used to
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be in the previous releases. With the default option, hotplug scripts
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will be launched by xl directly.
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Default: C<1>
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=item B<lockfile="PATH">
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Sets the path to the lock file used by xl to serialise certain
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operations (primarily domain creation).
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Default: C</var/lock/xl>
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=item B<vif.default.script="PATH">
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Configures the default hotplug script used by virtual network devices.
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The old B<vifscript> option is deprecated and should not be used.
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Default: C</etc/xen/scripts/vif-bridge>
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=item B<vif.default.bridge="NAME">
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Configures the default bridge to set for virtual network devices.
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The old B<defaultbridge> option is deprecated and should not be used.
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Default: C<xenbr0>
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=item B<vif.default.gatewaydev="NAME">
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Configures the default gateway device to set for virtual network devices.
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Default: C<None>
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=item B<output_format="json|sxp">
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Configures the default output format used by xl when printing "machine
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readable" information. The default is to use the C<JSON>
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L<http://www.json.org/> syntax. However for compatibility with the
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previous C<xm> toolstack this can be configured to use the old C<SXP>
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(S-Expression-like) syntax instead.
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Default: C<json>
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=item B<blkdev_start="NAME">
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Configures the name of the first block device to be used for temporary
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block device allocations by the toolstack.
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The default choice is "xvda".
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=item B<claim_mode=BOOLEAN>
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If this option is enabled then when a guest is created there will be an
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guarantee that there is memory available for the guest. This is an
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particularly acute problem on hosts with memory over-provisioned guests
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that use tmem and have self-balloon enabled (which is the default
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option). The self-balloon mechanism can deflate/inflate the balloon
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quickly and the amount of free memory (which C<xl info> can show) is
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stale the moment it is printed. When claim is enabled a reservation for
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the amount of memory (see 'memory' in xl.conf(5)) is set, which is then
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reduced as the domain's memory is populated and eventually reaches zero.
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The free memory in C<xl info> is the combination of the hypervisor's
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free heap memory minus the outstanding claims value.
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If the reservation cannot be meet the guest creation fails immediately
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instead of taking seconds/minutes (depending on the size of the guest)
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while the guest is populated.
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Note that to enable tmem type guests, one needs to provide C<tmem> on the
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Xen hypervisor argument and as well on the Linux kernel command line.
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Note that the claim call is not attempted if C<superpages> option is
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used in the guest config (see xl.cfg(5)).
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Default: C<0>
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=over 4
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=item C<0>
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No claim is made. Memory population during guest creation will be
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attempted as normal and may fail due to memory exhaustion.
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=item C<1>
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Normal memory and freeable pool of ephemeral pages (tmem) is used when
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calculating whether there is enough memory free to launch a guest.
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This guarantees immediate feedback whether the guest can be launched due
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to memory exhaustion (which can take a long time to find out if launching
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massively huge guests).
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=back
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=back
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=head1 SEE ALSO
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=over 4
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=item L<xl(1)>
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=item L<xl.cfg(5)>
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=item http://www.json.org/
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=back
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