File xenpaging.doc.patch of Package xen
--- docs/misc/xenpaging.txt | 66 +++++++++++++++++++++++++++++------------------- 1 file changed, 40 insertions(+), 26 deletions(-) Index: xen-4.1.2-testing/docs/misc/xenpaging.txt =================================================================== --- xen-4.1.2-testing.orig/docs/misc/xenpaging.txt +++ xen-4.1.2-testing/docs/misc/xenpaging.txt @@ -1,8 +1,6 @@ Warning: The xenpaging code is new and not fully debugged. -Usage of xenpaging can crash Xen or cause severe data corruption in the -guest memory and its filesystems! Description: @@ -14,34 +12,50 @@ than physically available on the host. Usage: -Once the guest is running, run xenpaging with the guest_id and the -number of pages to page-out: +To enable xenpaging for a guest add the option 'actmem=' to the guests +config file and run 'xm new <vm_config_file>' to make the changes +active. actmem= takes the amount of memory in MB which a guest is +allowed to use at a given time. Everything above this limit will be +paged out. This paging is transparent to the guest. + +Example: + memory=4096 + actmem=1024 +In this example a guest gets the impression it has 4GB of memory and +the guest OS has to configure itself for this amount of memory. But +xenpaging will page-out 3072MB, leaving only 1024MB active at a time. + +At runtime the configured value of actmem= can be changed with the "xm +mem-swap-target" command. + xm mem-swap-target <domain_name> 512 + +Additional cmdline options for the xenpaging binary can be specified +with the xenpaging_extra= config file option: + + xenpaging_extra=[ '-f', '/dev/shm/pagefile-guest_name', '-v' ] + +To get a list of available options, run /usr/lib/xen/bin/xenpaging -h: + + xenpaging [options] -f <pagefile> -d <domain_id> + +options: + -d <domid> --domain=<domid> numerical domain_id of guest. This option is required. + -f <file> --pagefile=<file> pagefile to use. This option is required. + -m <max_memkb> --max_memkb=<max_memkb> maximum amount of memory to handle. + -r <num> --mru_size=<num> number of paged-in pages to keep in memory. + -v --verbose enable debug output. + -h --help this output. + + +Caveats: +Live migration with a paged guest does currently not work, the guest +will crash once it starts on the target host. As a workaround stop +paging before starting the migration: - chdir /var/lib/xen/xenpaging - xenpaging <guest_id> <number_of_pages> - -To obtain the guest_id, run 'xm list'. -xenpaging will write the pagefile to the current directory. -Example with 128MB pagefile on guest 1: - - xenpaging 1 32768 - -Caution: stopping xenpaging manually will cause the guest to stall or -crash because the paged-out memory is not written back into the guest! - -After a reboot of a guest, its guest_id changes, the current xenpaging -binary has no target anymore. To automate restarting of xenpaging after -guest reboot, specify the number if pages in the guest configuration -file /etc/xen/vm/<guest_name>: - -xenpaging=32768 - -Redo the guest with 'xm create /etc/xen/vm/<guest_name>' to activate the -changes. +xm mem-swap-target <dom_name> 0 && xm migrate -l <dom_name> <remote_host> Todo: -- implement stopping of xenpaging - implement/test live migration
