view Documentation/usb/acm.txt @ 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
line source
1 Linux ACM driver v0.16
2 (c) 1999 Vojtech Pavlik <vojtech@suse.cz>
3 Sponsored by SuSE
4 ----------------------------------------------------------------------------
6 0. Disclaimer
7 ~~~~~~~~~~~~~
8 This program is free software; you can redistribute it and/or modify it
9 under the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 2 of the License, or (at your option)
11 any later version.
13 This program is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
16 more details.
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc., 59
20 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 Should you need to contact me, the author, you can do so either by e-mail
23 - mail your message to <vojtech@suse.cz>, or by paper mail: Vojtech Pavlik,
24 Ucitelska 1576, Prague 8, 182 00 Czech Republic
26 For your convenience, the GNU General Public License version 2 is included
27 in the package: See the file COPYING.
29 1. Usage
30 ~~~~~~~~
31 The drivers/usb/class/cdc-acm.c drivers works with USB modems and USB ISDN terminal
32 adapters that conform to the Universal Serial Bus Communication Device Class
33 Abstract Control Model (USB CDC ACM) specification.
35 Many modems do, here is a list of those I know of:
37 3Com OfficeConnect 56k
38 3Com Voice FaxModem Pro
39 3Com Sportster
40 MultiTech MultiModem 56k
41 Zoom 2986L FaxModem
42 Compaq 56k FaxModem
43 ELSA Microlink 56k
45 I know of one ISDN TA that does work with the acm driver:
47 3Com USR ISDN Pro TA
49 Unfortunately many modems and most ISDN TAs use proprietary interfaces and
50 thus won't work with this drivers. Check for ACM compliance before buying.
52 The driver (with devfs) creates these devices in /dev/usb/acm:
54 crw-r--r-- 1 root root 166, 0 Apr 1 10:49 0
55 crw-r--r-- 1 root root 166, 1 Apr 1 10:49 1
56 crw-r--r-- 1 root root 166, 2 Apr 1 10:49 2
58 And so on, up to 31, with the limit being possible to change in acm.c to up
59 to 256, so you can use up to 256 USB modems with one computer (you'll need
60 three USB cards for that, though).
62 If you don't use devfs, then you can create device nodes with the same
63 minor/major numbers anywhere you want, but either the above location or
64 /dev/usb/ttyACM0 is preferred.
66 To use the modems you need these modules loaded:
68 usbcore.ko
69 uhci-hcd.ko ohci-hcd.ko or ehci-hcd.ko
70 cdc-acm.ko
72 After that, the modem[s] should be accessible. You should be able to use
73 minicom, ppp and mgetty with them.
75 2. Verifying that it works
76 ~~~~~~~~~~~~~~~~~~~~~~~~~~
77 The first step would be to check /proc/bus/usb/devices, it should look
78 like this:
80 T: Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2
81 B: Alloc= 0/900 us ( 0%), #Int= 0, #Iso= 0
82 D: Ver= 1.00 Cls=09(hub ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
83 P: Vendor=0000 ProdID=0000 Rev= 0.00
84 S: Product=USB UHCI Root Hub
85 S: SerialNumber=6800
86 C:* #Ifs= 1 Cfg#= 1 Atr=40 MxPwr= 0mA
87 I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
88 E: Ad=81(I) Atr=03(Int.) MxPS= 8 Ivl=255ms
89 T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#= 2 Spd=12 MxCh= 0
90 D: Ver= 1.00 Cls=02(comm.) Sub=00 Prot=00 MxPS= 8 #Cfgs= 2
91 P: Vendor=04c1 ProdID=008f Rev= 2.07
92 S: Manufacturer=3Com Inc.
93 S: Product=3Com U.S. Robotics Pro ISDN TA
94 S: SerialNumber=UFT53A49BVT7
95 C: #Ifs= 1 Cfg#= 1 Atr=60 MxPwr= 0mA
96 I: If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=ff Prot=ff Driver=acm
97 E: Ad=85(I) Atr=02(Bulk) MxPS= 64 Ivl= 0ms
98 E: Ad=04(O) Atr=02(Bulk) MxPS= 64 Ivl= 0ms
99 E: Ad=81(I) Atr=03(Int.) MxPS= 16 Ivl=128ms
100 C:* #Ifs= 2 Cfg#= 2 Atr=60 MxPwr= 0mA
101 I: If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=02 Prot=01 Driver=acm
102 E: Ad=81(I) Atr=03(Int.) MxPS= 16 Ivl=128ms
103 I: If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=acm
104 E: Ad=85(I) Atr=02(Bulk) MxPS= 64 Ivl= 0ms
105 E: Ad=04(O) Atr=02(Bulk) MxPS= 64 Ivl= 0ms
107 The presence of these three lines (and the Cls= 'comm' and 'data' classes)
108 is important, it means it's an ACM device. The Driver=acm means the acm
109 driver is used for the device. If you see only Cls=ff(vend.) then you're out
110 of luck, you have a device with vendor specific-interface.
112 D: Ver= 1.00 Cls=02(comm.) Sub=00 Prot=00 MxPS= 8 #Cfgs= 2
113 I: If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=02 Prot=01 Driver=acm
114 I: If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=acm
116 In the system log you should see:
118 usb.c: USB new device connect, assigned device number 2
119 usb.c: kmalloc IF c7691fa0, numif 1
120 usb.c: kmalloc IF c7b5f3e0, numif 2
121 usb.c: skipped 4 class/vendor specific interface descriptors
122 usb.c: new device strings: Mfr=1, Product=2, SerialNumber=3
123 usb.c: USB device number 2 default language ID 0x409
124 Manufacturer: 3Com Inc.
125 Product: 3Com U.S. Robotics Pro ISDN TA
126 SerialNumber: UFT53A49BVT7
127 acm.c: probing config 1
128 acm.c: probing config 2
129 ttyACM0: USB ACM device
130 acm.c: acm_control_msg: rq: 0x22 val: 0x0 len: 0x0 result: 0
131 acm.c: acm_control_msg: rq: 0x20 val: 0x0 len: 0x7 result: 7
132 usb.c: acm driver claimed interface c7b5f3e0
133 usb.c: acm driver claimed interface c7b5f3f8
134 usb.c: acm driver claimed interface c7691fa0
136 If all this seems to be OK, fire up minicom and set it to talk to the ttyACM
137 device and try typing 'at'. If it responds with 'OK', then everything is
138 working.