ia64/linux-2.6.18-xen.hg

view arch/mips/sgi-ip27/ip27-reset.c @ 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 * This file is subject to the terms and conditions of the GNU General Public
3 * License. See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Reset an IP27.
7 *
8 * Copyright (C) 1997, 1998, 1999, 2000, 06 by Ralf Baechle
9 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
10 */
11 #include <linux/kernel.h>
12 #include <linux/sched.h>
13 #include <linux/timer.h>
14 #include <linux/smp.h>
15 #include <linux/mmzone.h>
16 #include <linux/nodemask.h>
17 #include <linux/pm.h>
19 #include <asm/io.h>
20 #include <asm/irq.h>
21 #include <asm/reboot.h>
22 #include <asm/system.h>
23 #include <asm/sgialib.h>
24 #include <asm/sn/addrs.h>
25 #include <asm/sn/arch.h>
26 #include <asm/sn/gda.h>
27 #include <asm/sn/sn0/hub.h>
29 void machine_restart(char *command) __attribute__((noreturn));
30 void machine_halt(void) __attribute__((noreturn));
31 void machine_power_off(void) __attribute__((noreturn));
33 #define noreturn while(1); /* Silence gcc. */
35 /* XXX How to pass the reboot command to the firmware??? */
36 static void ip27_machine_restart(char *command)
37 {
38 #if 0
39 int i;
40 #endif
42 printk("Reboot started from CPU %d\n", smp_processor_id());
43 #ifdef CONFIG_SMP
44 smp_send_stop();
45 #endif
46 #if 0
47 for_each_online_node(i)
48 REMOTE_HUB_S(COMPACT_TO_NASID_NODEID(i), PROMOP_REG,
49 PROMOP_REBOOT);
50 #else
51 LOCAL_HUB_S(NI_PORT_RESET, NPR_PORTRESET | NPR_LOCALRESET);
52 #endif
53 noreturn;
54 }
56 static void ip27_machine_halt(void)
57 {
58 int i;
60 #ifdef CONFIG_SMP
61 smp_send_stop();
62 #endif
63 for_each_online_node(i)
64 REMOTE_HUB_S(COMPACT_TO_NASID_NODEID(i), PROMOP_REG,
65 PROMOP_RESTART);
66 LOCAL_HUB_S(NI_PORT_RESET, NPR_PORTRESET | NPR_LOCALRESET);
67 noreturn;
68 }
70 static void ip27_machine_power_off(void)
71 {
72 /* To do ... */
73 noreturn;
74 }
76 void ip27_reboot_setup(void)
77 {
78 _machine_restart = ip27_machine_restart;
79 _machine_halt = ip27_machine_halt;
80 pm_power_off = ip27_machine_power_off;
81 }