ia64/linux-2.6.18-xen.hg

view drivers/net/ppp_mppe.h @ 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 #define MPPE_PAD 4 /* MPPE growth per frame */
2 #define MPPE_MAX_KEY_LEN 16 /* largest key length (128-bit) */
4 /* option bits for ccp_options.mppe */
5 #define MPPE_OPT_40 0x01 /* 40 bit */
6 #define MPPE_OPT_128 0x02 /* 128 bit */
7 #define MPPE_OPT_STATEFUL 0x04 /* stateful mode */
8 /* unsupported opts */
9 #define MPPE_OPT_56 0x08 /* 56 bit */
10 #define MPPE_OPT_MPPC 0x10 /* MPPC compression */
11 #define MPPE_OPT_D 0x20 /* Unknown */
12 #define MPPE_OPT_UNSUPPORTED (MPPE_OPT_56|MPPE_OPT_MPPC|MPPE_OPT_D)
13 #define MPPE_OPT_UNKNOWN 0x40 /* Bits !defined in RFC 3078 were set */
15 /*
16 * This is not nice ... the alternative is a bitfield struct though.
17 * And unfortunately, we cannot share the same bits for the option
18 * names above since C and H are the same bit. We could do a u_int32
19 * but then we have to do a htonl() all the time and/or we still need
20 * to know which octet is which.
21 */
22 #define MPPE_C_BIT 0x01 /* MPPC */
23 #define MPPE_D_BIT 0x10 /* Obsolete, usage unknown */
24 #define MPPE_L_BIT 0x20 /* 40-bit */
25 #define MPPE_S_BIT 0x40 /* 128-bit */
26 #define MPPE_M_BIT 0x80 /* 56-bit, not supported */
27 #define MPPE_H_BIT 0x01 /* Stateless (in a different byte) */
29 /* Does not include H bit; used for least significant octet only. */
30 #define MPPE_ALL_BITS (MPPE_D_BIT|MPPE_L_BIT|MPPE_S_BIT|MPPE_M_BIT|MPPE_H_BIT)
32 /* Build a CI from mppe opts (see RFC 3078) */
33 #define MPPE_OPTS_TO_CI(opts, ci) \
34 do { \
35 u_char *ptr = ci; /* u_char[4] */ \
36 \
37 /* H bit */ \
38 if (opts & MPPE_OPT_STATEFUL) \
39 *ptr++ = 0x0; \
40 else \
41 *ptr++ = MPPE_H_BIT; \
42 *ptr++ = 0; \
43 *ptr++ = 0; \
44 \
45 /* S,L bits */ \
46 *ptr = 0; \
47 if (opts & MPPE_OPT_128) \
48 *ptr |= MPPE_S_BIT; \
49 if (opts & MPPE_OPT_40) \
50 *ptr |= MPPE_L_BIT; \
51 /* M,D,C bits not supported */ \
52 } while (/* CONSTCOND */ 0)
54 /* The reverse of the above */
55 #define MPPE_CI_TO_OPTS(ci, opts) \
56 do { \
57 u_char *ptr = ci; /* u_char[4] */ \
58 \
59 opts = 0; \
60 \
61 /* H bit */ \
62 if (!(ptr[0] & MPPE_H_BIT)) \
63 opts |= MPPE_OPT_STATEFUL; \
64 \
65 /* S,L bits */ \
66 if (ptr[3] & MPPE_S_BIT) \
67 opts |= MPPE_OPT_128; \
68 if (ptr[3] & MPPE_L_BIT) \
69 opts |= MPPE_OPT_40; \
70 \
71 /* M,D,C bits */ \
72 if (ptr[3] & MPPE_M_BIT) \
73 opts |= MPPE_OPT_56; \
74 if (ptr[3] & MPPE_D_BIT) \
75 opts |= MPPE_OPT_D; \
76 if (ptr[3] & MPPE_C_BIT) \
77 opts |= MPPE_OPT_MPPC; \
78 \
79 /* Other bits */ \
80 if (ptr[0] & ~MPPE_H_BIT) \
81 opts |= MPPE_OPT_UNKNOWN; \
82 if (ptr[1] || ptr[2]) \
83 opts |= MPPE_OPT_UNKNOWN; \
84 if (ptr[3] & ~MPPE_ALL_BITS) \
85 opts |= MPPE_OPT_UNKNOWN; \
86 } while (/* CONSTCOND */ 0)