1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
|
/******************************************************************************
*
* Xen domain paging default policy.
*
* Copyright (c) 2009 Citrix Systems, Inc. (Patrick Colp)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "xc_bitops.h"
#include "policy.h"
#define DEFAULT_MRU_SIZE (1024 * 16)
static unsigned long *mru;
static unsigned int i_mru;
static unsigned int mru_size;
static unsigned long *bitmap;
static unsigned long *unconsumed;
static unsigned int unconsumed_cleared;
static unsigned long current_gfn;
static unsigned long max_pages;
int policy_init(struct xenpaging *paging)
{
int i;
int rc = -ENOMEM;
max_pages = paging->max_pages;
/* Allocate bitmap for pages not to page out */
bitmap = bitmap_alloc(max_pages);
if ( !bitmap )
goto out;
/* Allocate bitmap to track unusable pages */
unconsumed = bitmap_alloc(max_pages);
if ( !unconsumed )
goto out;
/* Initialise MRU list of paged in pages */
if ( paging->policy_mru_size > 0 )
mru_size = paging->policy_mru_size;
else
mru_size = paging->policy_mru_size = DEFAULT_MRU_SIZE;
mru = malloc(sizeof(*mru) * mru_size);
if ( mru == NULL )
goto out;
for ( i = 0; i < mru_size; i++ )
mru[i] = INVALID_MFN;
/* Don't page out page 0 */
set_bit(0, bitmap);
/* Start in the middle to avoid paging during BIOS startup */
current_gfn = max_pages / 2;
rc = 0;
out:
return rc;
}
unsigned long policy_choose_victim(struct xenpaging *paging)
{
xc_interface *xch = paging->xc_handle;
unsigned long i;
/* One iteration over all possible gfns */
for ( i = 0; i < max_pages; i++ )
{
/* Try next gfn */
current_gfn++;
/* Restart on wrap */
if ( current_gfn >= max_pages )
current_gfn = 0;
if ( (current_gfn & (BITS_PER_LONG - 1)) == 0 )
{
/* All gfns busy */
if ( ~bitmap[current_gfn >> ORDER_LONG] == 0 || ~unconsumed[current_gfn >> ORDER_LONG] == 0 )
{
current_gfn += BITS_PER_LONG;
i += BITS_PER_LONG;
continue;
}
}
/* gfn busy */
if ( test_bit(current_gfn, bitmap) )
continue;
/* gfn already tested */
if ( test_bit(current_gfn, unconsumed) )
continue;
/* gfn found */
break;
}
/* Could not nominate any gfn */
if ( i >= max_pages )
{
/* No more pages, wait in poll */
paging->use_poll_timeout = 1;
/* Count wrap arounds */
unconsumed_cleared++;
/* Force retry every few seconds (depends on poll() timeout) */
if ( unconsumed_cleared > 123)
{
/* Force retry of unconsumed gfns on next call */
bitmap_clear(unconsumed, max_pages);
unconsumed_cleared = 0;
DPRINTF("clearing unconsumed, current_gfn %lx", current_gfn);
}
return INVALID_MFN;
}
set_bit(current_gfn, unconsumed);
return current_gfn;
}
void policy_notify_paged_out(unsigned long gfn)
{
set_bit(gfn, bitmap);
clear_bit(gfn, unconsumed);
}
static void policy_handle_paged_in(unsigned long gfn, int do_mru)
{
unsigned long old_gfn = mru[i_mru & (mru_size - 1)];
if ( old_gfn != INVALID_MFN )
clear_bit(old_gfn, bitmap);
if (do_mru) {
mru[i_mru & (mru_size - 1)] = gfn;
} else {
clear_bit(gfn, bitmap);
mru[i_mru & (mru_size - 1)] = INVALID_MFN;
}
i_mru++;
}
void policy_notify_paged_in(unsigned long gfn)
{
policy_handle_paged_in(gfn, 1);
}
void policy_notify_paged_in_nomru(unsigned long gfn)
{
policy_handle_paged_in(gfn, 0);
}
void policy_notify_dropped(unsigned long gfn)
{
clear_bit(gfn, bitmap);
}
/*
* Local variables:
* mode: C
* c-file-style: "BSD"
* c-basic-offset: 4
* tab-width: 4
* indent-tabs-mode: nil
* End:
*/
|
