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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/man/xl.conf.pod.5 | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/docs/man/xl.conf.pod.5 b/docs/man/xl.conf.pod.5 index aaf8da1598..c4072aa7e4 100644 --- a/docs/man/xl.conf.pod.5 +++ b/docs/man/xl.conf.pod.5 @@ -115,6 +115,47 @@ Configures the name of the first block device to be used for temporary block device allocations by the toolstack. The default choice is "xvda". +=item B<claim_mode=BOOLEAN> + +If this option is enabled then when a guest is created there will be an +guarantee that there is memory available for the guest. This is an +particularly acute problem on hosts with memory over-provisioned guests +that use tmem and have self-balloon enabled (which is the default +option). The self-balloon mechanism can deflate/inflate the balloon +quickly and the amount of free memory (which C<xl info> can show) is +stale the moment it is printed. When claim is enabled a reservation for +the amount of memory (see 'memory' in xl.conf(5)) is set, which is then +reduced as the domain's memory is populated and eventually reaches zero. + +If the reservation cannot be meet the guest creation fails immediately +instead of taking seconds/minutes (depending on the size of the guest) +while the guest is populated. + +Note that to enable tmem type guests, one needs to provide C<tmem> on the +Xen hypervisor argument and as well on the Linux kernel command line. + +Note that the claim call is not attempted if C<superpages> option is +used in the guest config (see xl.cfg(5)). + +Default: C<0> + +=over 4 + +=item C<0> + +No claim is made. Memory population during guest creation will be +attempted as normal and may fail due to memory exhaustion. + +=item C<1> + +Normal memory and freeable pool of ephemeral pages (tmem) is used when +calculating whether there is enough memory free to launch a guest. +This guarantees immediate feedback whether the guest can be launched due +to memory exhaustion (which can take a long time to find out if launching +massively huge guests). + +=back + =back =head1 SEE ALSO |