ia64/linux-2.6.18-xen.hg

view arch/sparc/lib/strlen_user.S @ 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 /* strlen_user.S: Sparc optimized strlen_user code
2 *
3 * Return length of string in userspace including terminating 0
4 * or 0 for error
5 *
6 * Copyright (C) 1991,1996 Free Software Foundation
7 * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
8 * Copyright (C) 1996 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
9 */
11 #define LO_MAGIC 0x01010101
12 #define HI_MAGIC 0x80808080
14 10:
15 ldub [%o0], %o5
16 cmp %o5, 0
17 be 1f
18 add %o0, 1, %o0
19 andcc %o0, 3, %g0
20 be 4f
21 or %o4, %lo(HI_MAGIC), %o3
22 11:
23 ldub [%o0], %o5
24 cmp %o5, 0
25 be 2f
26 add %o0, 1, %o0
27 andcc %o0, 3, %g0
28 be 5f
29 sethi %hi(LO_MAGIC), %o4
30 12:
31 ldub [%o0], %o5
32 cmp %o5, 0
33 be 3f
34 add %o0, 1, %o0
35 b 13f
36 or %o4, %lo(LO_MAGIC), %o2
37 1:
38 retl
39 mov 1, %o0
40 2:
41 retl
42 mov 2, %o0
43 3:
44 retl
45 mov 3, %o0
47 .align 4
48 .global __strlen_user, __strnlen_user
49 __strlen_user:
50 sethi %hi(32768), %o1
51 __strnlen_user:
52 mov %o1, %g1
53 mov %o0, %o1
54 andcc %o0, 3, %g0
55 bne 10b
56 sethi %hi(HI_MAGIC), %o4
57 or %o4, %lo(HI_MAGIC), %o3
58 4:
59 sethi %hi(LO_MAGIC), %o4
60 5:
61 or %o4, %lo(LO_MAGIC), %o2
62 13:
63 ld [%o0], %o5
64 2:
65 sub %o5, %o2, %o4
66 andcc %o4, %o3, %g0
67 bne 82f
68 add %o0, 4, %o0
69 sub %o0, %o1, %g2
70 81: cmp %g2, %g1
71 blu 13b
72 mov %o0, %o4
73 ba,a 1f
75 /* Check every byte. */
76 82: srl %o5, 24, %g5
77 andcc %g5, 0xff, %g0
78 be 1f
79 add %o0, -3, %o4
80 srl %o5, 16, %g5
81 andcc %g5, 0xff, %g0
82 be 1f
83 add %o4, 1, %o4
84 srl %o5, 8, %g5
85 andcc %g5, 0xff, %g0
86 be 1f
87 add %o4, 1, %o4
88 andcc %o5, 0xff, %g0
89 bne 81b
90 sub %o0, %o1, %g2
92 add %o4, 1, %o4
93 1:
94 retl
95 sub %o4, %o1, %o0
97 .section .fixup,#alloc,#execinstr
98 .align 4
99 9:
100 retl
101 clr %o0
103 .section __ex_table,#alloc
104 .align 4
106 .word 10b, 9b
107 .word 11b, 9b
108 .word 12b, 9b
109 .word 13b, 9b