ia64/linux-2.6.18-xen.hg

view arch/mips/arc/file.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 * ARC firmware interface.
7 *
8 * Copyright (C) 1994, 1995, 1996, 1999 Ralf Baechle
9 * Copyright (C) 1999 Silicon Graphics, Inc.
10 */
11 #include <linux/init.h>
13 #include <asm/arc/types.h>
14 #include <asm/sgialib.h>
16 LONG __init
17 ArcGetDirectoryEntry(ULONG FileID, struct linux_vdirent *Buffer,
18 ULONG N, ULONG *Count)
19 {
20 return ARC_CALL4(get_vdirent, FileID, Buffer, N, Count);
21 }
23 LONG __init
24 ArcOpen(CHAR *Path, enum linux_omode OpenMode, ULONG *FileID)
25 {
26 return ARC_CALL3(open, Path, OpenMode, FileID);
27 }
29 LONG __init
30 ArcClose(ULONG FileID)
31 {
32 return ARC_CALL1(close, FileID);
33 }
35 LONG __init
36 ArcRead(ULONG FileID, VOID *Buffer, ULONG N, ULONG *Count)
37 {
38 return ARC_CALL4(read, FileID, Buffer, N, Count);
39 }
41 LONG __init
42 ArcGetReadStatus(ULONG FileID)
43 {
44 return ARC_CALL1(get_rstatus, FileID);
45 }
47 LONG __init
48 ArcWrite(ULONG FileID, PVOID Buffer, ULONG N, PULONG Count)
49 {
50 return ARC_CALL4(write, FileID, Buffer, N, Count);
51 }
53 LONG __init
54 ArcSeek(ULONG FileID, struct linux_bigint *Position, enum linux_seekmode SeekMode)
55 {
56 return ARC_CALL3(seek, FileID, Position, SeekMode);
57 }
59 LONG __init
60 ArcMount(char *name, enum linux_mountops op)
61 {
62 return ARC_CALL2(mount, name, op);
63 }
65 LONG __init
66 ArcGetFileInformation(ULONG FileID, struct linux_finfo *Information)
67 {
68 return ARC_CALL2(get_finfo, FileID, Information);
69 }
71 LONG __init ArcSetFileInformation(ULONG FileID, ULONG AttributeFlags,
72 ULONG AttributeMask)
73 {
74 return ARC_CALL3(set_finfo, FileID, AttributeFlags, AttributeMask);
75 }