view drivers/atm/zeprom.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
line source
1 /* drivers/atm/zeprom.h - ZeitNet ZN122x EEPROM (NM93C46) declarations */
3 /* Written 1995,1996 by Werner Almesberger, EPFL LRC */
9 /* Different versions use different control registers */
11 #define ZEPROM_V1_REG PCI_VENDOR_ID /* PCI register */
12 #define ZEPROM_V2_REG 0x40
14 /* Bits in contol register */
16 #define ZEPROM_SK 0x80000000 /* strobe (probably on raising edge) */
17 #define ZEPROM_CS 0x40000000 /* Chip Select */
18 #define ZEPROM_DI 0x20000000 /* Data Input */
19 #define ZEPROM_DO 0x10000000 /* Data Output */
21 #define ZEPROM_SIZE 32 /* 32 bytes */
22 #define ZEPROM_V1_ESI_OFF 24 /* ESI offset in EEPROM (V1) */
23 #define ZEPROM_V2_ESI_OFF 4 /* ESI offset in EEPROM (V2) */
25 #define ZEPROM_CMD_LEN 3 /* commands are three bits */
26 #define ZEPROM_ADDR_LEN 6 /* addresses are six bits */
28 /* Commands (3 bits) */
30 #define ZEPROM_CMD_READ 6
32 /* No other commands are needed. */
34 #endif