kernel_optimize_test/Documentation/ABI/stable/sysfs-devices-system-xen_memory
Marek Marczykowski-Górecki 197ecb3802 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>
2018-09-14 08:51:10 -04:00

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What: /sys/devices/system/xen_memory/xen_memory0/max_retry_count
Date: May 2011
KernelVersion: 2.6.39
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
The maximum number of times the balloon driver will
attempt to increase the balloon before giving up. See
also 'retry_count' below.
A value of zero means retry forever and is the default one.
What: /sys/devices/system/xen_memory/xen_memory0/max_schedule_delay
Date: May 2011
KernelVersion: 2.6.39
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
The limit that 'schedule_delay' (see below) will be
increased to. The default value is 32 seconds.
What: /sys/devices/system/xen_memory/xen_memory0/retry_count
Date: May 2011
KernelVersion: 2.6.39
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
The current number of times that the balloon driver
has attempted to increase the size of the balloon.
The default value is one. With max_retry_count being
zero (unlimited), this means that the driver will attempt
to retry with a 'schedule_delay' delay.
What: /sys/devices/system/xen_memory/xen_memory0/schedule_delay
Date: May 2011
KernelVersion: 2.6.39
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
The time (in seconds) to wait between attempts to
increase the balloon. Each time the balloon cannot be
increased, 'schedule_delay' is increased (until
'max_schedule_delay' is reached at which point it
will use the max value).
What: /sys/devices/system/xen_memory/xen_memory0/target
Date: April 2008
KernelVersion: 2.6.26
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
The target number of pages to adjust this domain's
memory reservation to.
What: /sys/devices/system/xen_memory/xen_memory0/target_kb
Date: April 2008
KernelVersion: 2.6.26
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
As target above, except the value is in KiB.
What: /sys/devices/system/xen_memory/xen_memory0/info/current_kb
Date: April 2008
KernelVersion: 2.6.26
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
Current size (in KiB) of this domain's memory
reservation.
What: /sys/devices/system/xen_memory/xen_memory0/info/high_kb
Date: April 2008
KernelVersion: 2.6.26
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
Amount (in KiB) of high memory in the balloon.
What: /sys/devices/system/xen_memory/xen_memory0/info/low_kb
Date: April 2008
KernelVersion: 2.6.26
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.