ia64/linux-2.6.18-xen.hg

view drivers/atm/tonga.h @ 897:329ea0ccb344

balloon: try harder to balloon up under memory pressure.

Currently if the balloon driver is unable to increase the guest's
reservation it assumes the failure was due to reaching its full
allocation, gives up on the ballooning operation and records the limit
it reached as the "hard limit". The driver will not try again until
the target is set again (even to the same value).

However it is possible that ballooning has in fact failed due to
memory pressure in the host and therefore it is desirable to keep
attempting to reach the target in case memory becomes available. The
most likely scenario is that some guests are ballooning down while
others are ballooning up and therefore there is temporary memory
pressure while things stabilise. You would not expect a well behaved
toolstack to ask a domain to balloon to more than its allocation nor
would you expect it to deliberately over-commit memory by setting
balloon targets which exceed the total host memory.

This patch drops the concept of a hard limit and causes the balloon
driver to retry increasing the reservation on a timer in the same
manner as when decreasing the reservation.

Also if we partially succeed in increasing the reservation
(i.e. receive less pages than we asked for) then we may as well keep
those pages rather than returning them to Xen.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Fri Jun 05 14:01:20 2009 +0100 (2009-06-05)
parents 831230e53067
children
line source
1 /* drivers/atm/tonga.h - Efficient Networks Tonga (PCI bridge) declarations */
3 /* Written 1995 by Werner Almesberger, EPFL LRC */
6 #ifndef DRIVER_ATM_TONGA_H
7 #define DRIVER_ATM_TONGA_H
9 #define PCI_TONGA_CTRL 0x60 /* control register */
11 #define END_SWAP_DMA 0x80 /* endian swap on DMA */
12 #define END_SWAP_BYTE 0x40 /* endian swap on slave byte accesses */
13 #define END_SWAP_WORD 0x20 /* endian swap on slave word accesses */
14 #define SEPROM_MAGIC 0x0c /* obscure required pattern (ASIC only) */
15 #define SEPROM_DATA 0x02 /* serial EEPROM data (ASIC only) */
16 #define SEPROM_CLK 0x01 /* serial EEPROM clock (ASIC only) */
18 #define SEPROM_ESI_BASE 64 /* start of ESI in serial EEPROM */
20 #endif