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| author |   Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> | 2018-09-07 18:49:08 +0200 |
|---|---|---|
| committer |   Boris Ostrovsky <boris.ostrovsky@oracle.com> | 2018-09-14 08:51:10 -0400 |
| commit | 197ecb3802c04499d8ff4f8cb28f6efa008067db (patch) | |
| tree | 1041826ddc2a9de936923f3563a6e51fefac7511 /Documentation | |
| parent | xen/manage: don't complain about an empty value in control/sysrq node (diff) | |
| download | linux-dev-197ecb3802c04499d8ff4f8cb28f6efa008067db.tar.xz linux-dev-197ecb3802c04499d8ff4f8cb28f6efa008067db.zip | |
xen/balloon: add runtime control for scrubbing ballooned out pages
Scrubbing pages on initial balloon down can take some time, especially
in nested virtualization case (nested EPT is slow). When HVM/PVH guest is
started with memory= significantly lower than maxmem=, all the extra
pages will be scrubbed before returning to Xen. But since most of them
weren't used at all at that point, Xen needs to populate them first
(from populate-on-demand pool). In nested virt case (Xen inside KVM)
this slows down the guest boot by 15-30s with just 1.5GB needed to be
returned to Xen.
Add runtime parameter to enable/disable it, to allow initially disabling
scrubbing, then enable it back during boot (for example in initramfs).
Such usage relies on assumption that a) most pages ballooned out during
initial boot weren't used at all, and b) even if they were, very few
secrets are in the guest at that time (before any serious userspace
kicks in).
Convert CONFIG_XEN_SCRUB_PAGES to CONFIG_XEN_SCRUB_PAGES_DEFAULT (also
enabled by default), controlling default value for the new runtime
switch.
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/stable/sysfs-devices-system-xen_memory | 9 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 6 |
2 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/ABI/stable/sysfs-devices-system-xen_memory b/Documentation/ABI/stable/sysfs-devices-system-xen_memory index caa311d59ac1..6d83f95a8a8e 100644 --- a/Documentation/ABI/stable/sysfs-devices-system-xen_memory +++ b/Documentation/ABI/stable/sysfs-devices-system-xen_memory @@ -75,3 +75,12 @@ Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Description: Amount (in KiB) of low (or normal) memory in the balloon. + +What: /sys/devices/system/xen_memory/xen_memory0/scrub_pages +Date: September 2018 +KernelVersion: 4.20 +Contact: xen-devel@lists.xenproject.org +Description: + Control scrubbing pages before returning them to Xen for others domains + use. Can be set with xen_scrub_pages cmdline + parameter. Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 64a3bf54b974..92eb1f42240d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5000,6 +5000,12 @@ Disables the PV optimizations forcing the HVM guest to run as generic HVM guest with no PV drivers. + xen_scrub_pages= [XEN] + Boolean option to control scrubbing pages before giving them back + to Xen, for use by other domains. Can be also changed at runtime + with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. + Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. + xirc2ps_cs= [NET,PCMCIA] Format: <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] |