view drivers/net/dgrs.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 /*
2 * ioctl's for the Digi Intl. RightSwitch
3 *
4 * These network driver ioctl's are a bit obtuse compared to the usual
5 * ioctl's for a "normal" device driver. Hey, I didn't invent it.
6 *
7 * Typical use:
8 *
9 * struct ifreq ifr;
10 * DGRS_IOCTL ioc;
11 * int x;
12 *
13 * strcpy(ifr.ifr_name, "eth1");
14 * ifr.ifr_data = (caddr_t) &ioc;
15 * ioc.cmd = DGRS_GETMEM;
16 * ioc.len = sizeof(x);
17 * ioc.data = (caddr_t) &x;
18 * rc = ioctl(fd, DGRSIOCTL, &ifr);
19 * printf("rc=%d mem=%x\n", rc, x);
20 *
21 */
22 #include <linux/sockios.h>
26 typedef struct dgrs_ioctl {
27 unsigned short cmd; /* Command to run */
28 unsigned short len; /* Length of the data buffer */
29 unsigned char __user *data; /* Pointer to the data buffer */
30 unsigned short port; /* port number for command, if needed */
31 unsigned short filter; /* filter number for command, if needed */
34 /*
35 * Commands for the driver
36 */
37 #define DGRS_GETMEM 0x01 /* Get the dual port memory address */
38 #define DGRS_SETFILTER 0x02 /* Set a filter */