ia64/linux-2.6.18-xen.hg

view drivers/acpi/namespace/nsnames.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 *
3 * Module Name: nsnames - Name manipulation and search
4 *
5 ******************************************************************************/
7 /*
8 * Copyright (C) 2000 - 2006, R. Byron Moore
9 * All rights reserved.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions, and the following disclaimer,
16 * without modification.
17 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
18 * substantially similar to the "NO WARRANTY" disclaimer below
19 * ("Disclaimer") and any redistribution must be conditioned upon
20 * including a substantially similar Disclaimer requirement for further
21 * binary redistribution.
22 * 3. Neither the names of the above-listed copyright holders nor the names
23 * of any contributors may be used to endorse or promote products derived
24 * from this software without specific prior written permission.
25 *
26 * Alternatively, this software may be distributed under the terms of the
27 * GNU General Public License ("GPL") version 2 as published by the Free
28 * Software Foundation.
29 *
30 * NO WARRANTY
31 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
32 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
33 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
34 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
35 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
40 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
41 * POSSIBILITY OF SUCH DAMAGES.
42 */
44 #include <acpi/acpi.h>
45 #include <acpi/amlcode.h>
46 #include <acpi/acnamesp.h>
48 #define _COMPONENT ACPI_NAMESPACE
49 ACPI_MODULE_NAME("nsnames")
51 /*******************************************************************************
52 *
53 * FUNCTION: acpi_ns_build_external_path
54 *
55 * PARAMETERS: Node - NS node whose pathname is needed
56 * Size - Size of the pathname
57 * *name_buffer - Where to return the pathname
58 *
59 * RETURN: Places the pathname into the name_buffer, in external format
60 * (name segments separated by path separators)
61 *
62 * DESCRIPTION: Generate a full pathaname
63 *
64 ******************************************************************************/
65 void
66 acpi_ns_build_external_path(struct acpi_namespace_node *node,
67 acpi_size size, char *name_buffer)
68 {
69 acpi_size index;
70 struct acpi_namespace_node *parent_node;
72 ACPI_FUNCTION_ENTRY();
74 /* Special case for root */
76 index = size - 1;
77 if (index < ACPI_NAME_SIZE) {
78 name_buffer[0] = AML_ROOT_PREFIX;
79 name_buffer[1] = 0;
80 return;
81 }
83 /* Store terminator byte, then build name backwards */
85 parent_node = node;
86 name_buffer[index] = 0;
88 while ((index > ACPI_NAME_SIZE) && (parent_node != acpi_gbl_root_node)) {
89 index -= ACPI_NAME_SIZE;
91 /* Put the name into the buffer */
93 ACPI_MOVE_32_TO_32((name_buffer + index), &parent_node->name);
94 parent_node = acpi_ns_get_parent_node(parent_node);
96 /* Prefix name with the path separator */
98 index--;
99 name_buffer[index] = ACPI_PATH_SEPARATOR;
100 }
102 /* Overwrite final separator with the root prefix character */
104 name_buffer[index] = AML_ROOT_PREFIX;
106 if (index != 0) {
107 ACPI_ERROR((AE_INFO,
108 "Could not construct pathname; index=%X, size=%X, Path=%s",
109 (u32) index, (u32) size, &name_buffer[size]));
110 }
112 return;
113 }
115 #ifdef ACPI_DEBUG_OUTPUT
116 /*******************************************************************************
117 *
118 * FUNCTION: acpi_ns_get_external_pathname
119 *
120 * PARAMETERS: Node - Namespace node whose pathname is needed
121 *
122 * RETURN: Pointer to storage containing the fully qualified name of
123 * the node, In external format (name segments separated by path
124 * separators.)
125 *
126 * DESCRIPTION: Used for debug printing in acpi_ns_search_table().
127 *
128 ******************************************************************************/
130 char *acpi_ns_get_external_pathname(struct acpi_namespace_node *node)
131 {
132 char *name_buffer;
133 acpi_size size;
135 ACPI_FUNCTION_TRACE_PTR(ns_get_external_pathname, node);
137 /* Calculate required buffer size based on depth below root */
139 size = acpi_ns_get_pathname_length(node);
141 /* Allocate a buffer to be returned to caller */
143 name_buffer = ACPI_ALLOCATE_ZEROED(size);
144 if (!name_buffer) {
145 ACPI_ERROR((AE_INFO, "Allocation failure"));
146 return_PTR(NULL);
147 }
149 /* Build the path in the allocated buffer */
151 acpi_ns_build_external_path(node, size, name_buffer);
152 return_PTR(name_buffer);
153 }
154 #endif
156 /*******************************************************************************
157 *
158 * FUNCTION: acpi_ns_get_pathname_length
159 *
160 * PARAMETERS: Node - Namespace node
161 *
162 * RETURN: Length of path, including prefix
163 *
164 * DESCRIPTION: Get the length of the pathname string for this node
165 *
166 ******************************************************************************/
168 acpi_size acpi_ns_get_pathname_length(struct acpi_namespace_node *node)
169 {
170 acpi_size size;
171 struct acpi_namespace_node *next_node;
173 ACPI_FUNCTION_ENTRY();
175 /*
176 * Compute length of pathname as 5 * number of name segments.
177 * Go back up the parent tree to the root
178 */
179 size = 0;
180 next_node = node;
182 while (next_node && (next_node != acpi_gbl_root_node)) {
183 size += ACPI_PATH_SEGMENT_LENGTH;
184 next_node = acpi_ns_get_parent_node(next_node);
185 }
187 if (!size) {
188 size = 1; /* Root node case */
189 }
191 return (size + 1); /* +1 for null string terminator */
192 }
194 /*******************************************************************************
195 *
196 * FUNCTION: acpi_ns_handle_to_pathname
197 *
198 * PARAMETERS: target_handle - Handle of named object whose name is
199 * to be found
200 * Buffer - Where the pathname is returned
201 *
202 * RETURN: Status, Buffer is filled with pathname if status is AE_OK
203 *
204 * DESCRIPTION: Build and return a full namespace pathname
205 *
206 ******************************************************************************/
208 acpi_status
209 acpi_ns_handle_to_pathname(acpi_handle target_handle,
210 struct acpi_buffer * buffer)
211 {
212 acpi_status status;
213 struct acpi_namespace_node *node;
214 acpi_size required_size;
216 ACPI_FUNCTION_TRACE_PTR(ns_handle_to_pathname, target_handle);
218 node = acpi_ns_map_handle_to_node(target_handle);
219 if (!node) {
220 return_ACPI_STATUS(AE_BAD_PARAMETER);
221 }
223 /* Determine size required for the caller buffer */
225 required_size = acpi_ns_get_pathname_length(node);
227 /* Validate/Allocate/Clear caller buffer */
229 status = acpi_ut_initialize_buffer(buffer, required_size);
230 if (ACPI_FAILURE(status)) {
231 return_ACPI_STATUS(status);
232 }
234 /* Build the path in the caller buffer */
236 acpi_ns_build_external_path(node, required_size, buffer->pointer);
238 ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "%s [%X]\n",
239 (char *)buffer->pointer, (u32) required_size));
240 return_ACPI_STATUS(AE_OK);
241 }