view drivers/pci/setup-irq.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
line source
1 /*
2 * drivers/pci/setup-irq.c
3 *
4 * Extruded from code written by
5 * Dave Rusling (david.rusling@reo.mts.dec.com)
6 * David Mosberger (davidm@cs.arizona.edu)
7 * David Miller (davem@redhat.com)
8 *
9 * Support routines for initializing a PCI subsystem.
10 */
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/pci.h>
16 #include <linux/errno.h>
17 #include <linux/ioport.h>
18 #include <linux/cache.h>
21 static void __init
22 pdev_fixup_irq(struct pci_dev *dev,
23 u8 (*swizzle)(struct pci_dev *, u8 *),
24 int (*map_irq)(struct pci_dev *, u8, u8))
25 {
26 u8 pin, slot;
27 int irq;
29 /* If this device is not on the primary bus, we need to figure out
30 which interrupt pin it will come in on. We know which slot it
31 will come in on 'cos that slot is where the bridge is. Each
32 time the interrupt line passes through a PCI-PCI bridge we must
33 apply the swizzle function. */
35 pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin);
36 /* Cope with 0 and illegal. */
37 if (pin == 0 || pin > 4)
38 pin = 1;
40 /* Follow the chain of bridges, swizzling as we go. */
41 slot = (*swizzle)(dev, &pin);
43 irq = (*map_irq)(dev, slot, pin);
44 if (irq == -1)
45 irq = 0;
46 dev->irq = irq;
48 pr_debug("PCI: fixup irq: (%s) got %d\n",
49 dev->dev.kobj.name, dev->irq);
51 /* Always tell the device, so the driver knows what is
52 the real IRQ to use; the device does not use it. */
53 pcibios_update_irq(dev, irq);
54 }
56 void __init
57 pci_fixup_irqs(u8 (*swizzle)(struct pci_dev *, u8 *),
58 int (*map_irq)(struct pci_dev *, u8, u8))
59 {
60 struct pci_dev *dev = NULL;
61 while ((dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev)) != NULL) {
62 pdev_fixup_irq(dev, swizzle, map_irq);
63 }
64 }