ia64/linux-2.6.18-xen.hg

view drivers/serial/mcfserial.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 /*
2 * mcfserial.c -- serial driver for ColdFire internal UARTS.
3 *
4 * Copyright (c) 1999 Greg Ungerer <gerg@snapgear.com>
5 * Copyright (c) 2000-2001 Lineo, Inc. <www.lineo.com>
6 * Copyright (c) 2002 SnapGear Inc., <www.snapgear.com>
7 *
8 * Based on code from 68332serial.c which was:
9 *
10 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
11 * Copyright (C) 1998 TSHG
12 * Copyright (c) 1999 Rt-Control Inc. <jeff@uclinux.org>
13 */
14 #ifndef _MCF_SERIAL_H
15 #define _MCF_SERIAL_H
17 #include <linux/serial.h>
19 #ifdef __KERNEL__
21 /*
22 * Define a local serial stats structure.
23 */
25 struct mcf_stats {
26 unsigned int rx;
27 unsigned int tx;
28 unsigned int rxbreak;
29 unsigned int rxframing;
30 unsigned int rxparity;
31 unsigned int rxoverrun;
32 };
35 /*
36 * This is our internal structure for each serial port's state.
37 * Each serial port has one of these structures associated with it.
38 */
40 struct mcf_serial {
41 int magic;
42 volatile unsigned char *addr; /* UART memory address */
43 int irq;
44 int flags; /* defined in tty.h */
45 int type; /* UART type */
46 struct tty_struct *tty;
47 unsigned char imr; /* Software imr register */
48 unsigned int baud;
49 int sigs;
50 int custom_divisor;
51 int x_char; /* xon/xoff character */
52 int baud_base;
53 int close_delay;
54 unsigned short closing_wait;
55 unsigned short closing_wait2;
56 unsigned long event;
57 int line;
58 int count; /* # of fd on device */
59 int blocked_open; /* # of blocked opens */
60 unsigned char *xmit_buf;
61 int xmit_head;
62 int xmit_tail;
63 int xmit_cnt;
64 struct mcf_stats stats;
65 struct work_struct tqueue;
66 struct work_struct tqueue_hangup;
67 wait_queue_head_t open_wait;
68 wait_queue_head_t close_wait;
70 };
72 #endif /* __KERNEL__ */
74 #endif /* _MCF_SERIAL_H */