ia64/linux-2.6.18-xen.hg

view Documentation/networking/z8530drv.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
children
line source
1 This is a subset of the documentation. To use this driver you MUST have the
2 full package from:
4 Internet:
5 =========
7 1. ftp://ftp.ccac.rwth-aachen.de/pub/jr/z8530drv-utils_3.0-3.tar.gz
9 2. ftp://ftp.pspt.fi/pub/ham/linux/ax25/z8530drv-utils_3.0-3.tar.gz
11 Please note that the information in this document may be hopelessly outdated.
12 A new version of the documentation, along with links to other important
13 Linux Kernel AX.25 documentation and programs, is available on
14 http://yaina.de/jreuter
16 -----------------------------------------------------------------------------
19 SCC.C - Linux driver for Z8530 based HDLC cards for AX.25
21 ********************************************************************
23 (c) 1993,2000 by Joerg Reuter DL1BKE <jreuter@yaina.de>
25 portions (c) 1993 Guido ten Dolle PE1NNZ
27 for the complete copyright notice see >> Copying.Z8530DRV <<
29 ********************************************************************
32 1. Initialization of the driver
33 ===============================
35 To use the driver, 3 steps must be performed:
37 1. if compiled as module: loading the module
38 2. Setup of hardware, MODEM and KISS parameters with sccinit
39 3. Attach each channel to the Linux kernel AX.25 with "ifconfig"
41 Unlike the versions below 2.4 this driver is a real network device
42 driver. If you want to run xNOS instead of our fine kernel AX.25
43 use a 2.x version (available from above sites) or read the
44 AX.25-HOWTO on how to emulate a KISS TNC on network device drivers.
47 1.1 Loading the module
48 ======================
50 (If you're going to compile the driver as a part of the kernel image,
51 skip this chapter and continue with 1.2)
53 Before you can use a module, you'll have to load it with
55 insmod scc.o
57 please read 'man insmod' that comes with module-init-tools.
59 You should include the insmod in one of the /etc/rc.d/rc.* files,
60 and don't forget to insert a call of sccinit after that. It
61 will read your /etc/z8530drv.conf.
63 1.2. /etc/z8530drv.conf
64 =======================
66 To setup all parameters you must run /sbin/sccinit from one
67 of your rc.*-files. This has to be done BEFORE you can
68 "ifconfig" an interface. Sccinit reads the file /etc/z8530drv.conf
69 and sets the hardware, MODEM and KISS parameters. A sample file is
70 delivered with this package. Change it to your needs.
72 The file itself consists of two main sections.
74 1.2.1 configuration of hardware parameters
75 ==========================================
77 The hardware setup section defines the following parameters for each
78 Z8530:
80 chip 1
81 data_a 0x300 # data port A
82 ctrl_a 0x304 # control port A
83 data_b 0x301 # data port B
84 ctrl_b 0x305 # control port B
85 irq 5 # IRQ No. 5
86 pclock 4915200 # clock
87 board BAYCOM # hardware type
88 escc no # enhanced SCC chip? (8580/85180/85280)
89 vector 0 # latch for interrupt vector
90 special no # address of special function register
91 option 0 # option to set via sfr
94 chip - this is just a delimiter to make sccinit a bit simpler to
95 program. A parameter has no effect.
97 data_a - the address of the data port A of this Z8530 (needed)
98 ctrl_a - the address of the control port A (needed)
99 data_b - the address of the data port B (needed)
100 ctrl_b - the address of the control port B (needed)
102 irq - the used IRQ for this chip. Different chips can use different
103 IRQs or the same. If they share an interrupt, it needs to be
104 specified within one chip-definition only.
106 pclock - the clock at the PCLK pin of the Z8530 (option, 4915200 is
107 default), measured in Hertz
109 board - the "type" of the board:
111 SCC type value
112 ---------------------------------
113 PA0HZP SCC card PA0HZP
114 EAGLE card EAGLE
115 PC100 card PC100
116 PRIMUS-PC (DG9BL) card PRIMUS
117 BayCom (U)SCC card BAYCOM
119 escc - if you want support for ESCC chips (8580, 85180, 85280), set
120 this to "yes" (option, defaults to "no")
122 vector - address of the vector latch (aka "intack port") for PA0HZP
123 cards. There can be only one vector latch for all chips!
124 (option, defaults to 0)
126 special - address of the special function register on several cards.
127 (option, defaults to 0)
129 option - The value you write into that register (option, default is 0)
131 You can specify up to four chips (8 channels). If this is not enough,
132 just change
134 #define MAXSCC 4
136 to a higher value.
138 Example for the BAYCOM USCC:
139 ----------------------------
141 chip 1
142 data_a 0x300 # data port A
143 ctrl_a 0x304 # control port A
144 data_b 0x301 # data port B
145 ctrl_b 0x305 # control port B
146 irq 5 # IRQ No. 5 (#)
147 board BAYCOM # hardware type (*)
148 #
149 # SCC chip 2
150 #
151 chip 2
152 data_a 0x302
153 ctrl_a 0x306
154 data_b 0x303
155 ctrl_b 0x307
156 board BAYCOM
158 An example for a PA0HZP card:
159 -----------------------------
161 chip 1
162 data_a 0x153
163 data_b 0x151
164 ctrl_a 0x152
165 ctrl_b 0x150
166 irq 9
167 pclock 4915200
168 board PA0HZP
169 vector 0x168
170 escc no
171 #
172 #
173 #
174 chip 2
175 data_a 0x157
176 data_b 0x155
177 ctrl_a 0x156
178 ctrl_b 0x154
179 irq 9
180 pclock 4915200
181 board PA0HZP
182 vector 0x168
183 escc no
185 A DRSI would should probably work with this:
186 --------------------------------------------
187 (actually: two DRSI cards...)
189 chip 1
190 data_a 0x303
191 data_b 0x301
192 ctrl_a 0x302
193 ctrl_b 0x300
194 irq 7
195 pclock 4915200
196 board DRSI
197 escc no
198 #
199 #
200 #
201 chip 2
202 data_a 0x313
203 data_b 0x311
204 ctrl_a 0x312
205 ctrl_b 0x310
206 irq 7
207 pclock 4915200
208 board DRSI
209 escc no
211 Note that you cannot use the on-board baudrate generator off DRSI
212 cards. Use "mode dpll" for clock source (see below).
214 This is based on information provided by Mike Bilow (and verified
215 by Paul Helay)
217 The utility "gencfg"
218 --------------------
220 If you only know the parameters for the PE1CHL driver for DOS,
221 run gencfg. It will generate the correct port addresses (I hope).
222 Its parameters are exactly the same as the ones you use with
223 the "attach scc" command in net, except that the string "init" must
224 not appear. Example:
226 gencfg 2 0x150 4 2 0 1 0x168 9 4915200
228 will print a skeleton z8530drv.conf for the OptoSCC to stdout.
230 gencfg 2 0x300 2 4 5 -4 0 7 4915200 0x10
232 does the same for the BAYCOM USCC card. In my opinion it is much easier
233 to edit scc_config.h...
236 1.2.2 channel configuration
237 ===========================
239 The channel definition is divided into three sub sections for each
240 channel:
242 An example for scc0:
244 # DEVICE
246 device scc0 # the device for the following params
248 # MODEM / BUFFERS
250 speed 1200 # the default baudrate
251 clock dpll # clock source:
252 # dpll = normal half duplex operation
253 # external = MODEM provides own Rx/Tx clock
254 # divider = use full duplex divider if
255 # installed (1)
256 mode nrzi # HDLC encoding mode
257 # nrzi = 1k2 MODEM, G3RUH 9k6 MODEM
258 # nrz = DF9IC 9k6 MODEM
259 #
260 bufsize 384 # size of buffers. Note that this must include
261 # the AX.25 header, not only the data field!
262 # (optional, defaults to 384)
264 # KISS (Layer 1)
266 txdelay 36 # (see chapter 1.4)
267 persist 64
268 slot 8
269 tail 8
270 fulldup 0
271 wait 12
272 min 3
273 maxkey 7
274 idle 3
275 maxdef 120
276 group 0
277 txoff off
278 softdcd on
279 slip off
281 The order WITHIN these sections is unimportant. The order OF these
282 sections IS important. The MODEM parameters are set with the first
283 recognized KISS parameter...
285 Please note that you can initialize the board only once after boot
286 (or insmod). You can change all parameters but "mode" and "clock"
287 later with the Sccparam program or through KISS. Just to avoid
288 security holes...
290 (1) this divider is usually mounted on the SCC-PBC (PA0HZP) or not
291 present at all (BayCom). It feeds back the output of the DPLL
292 (digital pll) as transmit clock. Using this mode without a divider
293 installed will normally result in keying the transceiver until
294 maxkey expires --- of course without sending anything (useful).
296 2. Attachment of a channel by your AX.25 software
297 =================================================
299 2.1 Kernel AX.25
300 ================
302 To set up an AX.25 device you can simply type:
304 ifconfig scc0 44.128.1.1 hw ax25 dl0tha-7
306 This will create a network interface with the IP number 44.128.20.107
307 and the callsign "dl0tha". If you do not have any IP number (yet) you
308 can use any of the 44.128.0.0 network. Note that you do not need
309 axattach. The purpose of axattach (like slattach) is to create a KISS
310 network device linked to a TTY. Please read the documentation of the
311 ax25-utils and the AX.25-HOWTO to learn how to set the parameters of
312 the kernel AX.25.
314 2.2 NOS, NET and TFKISS
315 =======================
317 Since the TTY driver (aka KISS TNC emulation) is gone you need
318 to emulate the old behaviour. The cost of using these programs is
319 that you probably need to compile the kernel AX.25, regardless of whether
320 you actually use it or not. First setup your /etc/ax25/axports,
321 for example:
323 9k6 dl0tha-9 9600 255 4 9600 baud port (scc3)
324 axlink dl0tha-15 38400 255 4 Link to NOS
326 Now "ifconfig" the scc device:
328 ifconfig scc3 44.128.1.1 hw ax25 dl0tha-9
330 You can now axattach a pseudo-TTY:
332 axattach /dev/ptys0 axlink
334 and start your NOS and attach /dev/ptys0 there. The problem is that
335 NOS is reachable only via digipeating through the kernel AX.25
336 (disastrous on a DAMA controlled channel). To solve this problem,
337 configure "rxecho" to echo the incoming frames from "9k6" to "axlink"
338 and outgoing frames from "axlink" to "9k6" and start:
340 rxecho
342 Or simply use "kissbridge" coming with z8530drv-utils:
344 ifconfig scc3 hw ax25 dl0tha-9
345 kissbridge scc3 /dev/ptys0
348 3. Adjustment and Display of parameters
349 =======================================
351 3.1 Displaying SCC Parameters:
352 ==============================
354 Once a SCC channel has been attached, the parameter settings and
355 some statistic information can be shown using the param program:
357 dl1bke-u:~$ sccstat scc0
359 Parameters:
361 speed : 1200 baud
362 txdelay : 36
363 persist : 255
364 slottime : 0
365 txtail : 8
366 fulldup : 1
367 waittime : 12
368 mintime : 3 sec
369 maxkeyup : 7 sec
370 idletime : 3 sec
371 maxdefer : 120 sec
372 group : 0x00
373 txoff : off
374 softdcd : on
375 SLIP : off
377 Status:
379 HDLC Z8530 Interrupts Buffers
380 -----------------------------------------------------------------------
381 Sent : 273 RxOver : 0 RxInts : 125074 Size : 384
382 Received : 1095 TxUnder: 0 TxInts : 4684 NoSpace : 0
383 RxErrors : 1591 ExInts : 11776
384 TxErrors : 0 SpInts : 1503
385 Tx State : idle
388 The status info shown is:
390 Sent - number of frames transmitted
391 Received - number of frames received
392 RxErrors - number of receive errors (CRC, ABORT)
393 TxErrors - number of discarded Tx frames (due to various reasons)
394 Tx State - status of the Tx interrupt handler: idle/busy/active/tail (2)
395 RxOver - number of receiver overruns
396 TxUnder - number of transmitter underruns
397 RxInts - number of receiver interrupts
398 TxInts - number of transmitter interrupts
399 EpInts - number of receiver special condition interrupts
400 SpInts - number of external/status interrupts
401 Size - maximum size of an AX.25 frame (*with* AX.25 headers!)
402 NoSpace - number of times a buffer could not get allocated
404 An overrun is abnormal. If lots of these occur, the product of
405 baudrate and number of interfaces is too high for the processing
406 power of your computer. NoSpace errors are unlikely to be caused by the
407 driver or the kernel AX.25.
410 3.2 Setting Parameters
411 ======================
414 The setting of parameters of the emulated KISS TNC is done in the
415 same way in the SCC driver. You can change parameters by using
416 the kissparms program from the ax25-utils package or use the program
417 "sccparam":
419 sccparam <device> <paramname> <decimal-|hexadecimal value>
421 You can change the following parameters:
423 param : value
424 ------------------------
425 speed : 1200
426 txdelay : 36
427 persist : 255
428 slottime : 0
429 txtail : 8
430 fulldup : 1
431 waittime : 12
432 mintime : 3
433 maxkeyup : 7
434 idletime : 3
435 maxdefer : 120
436 group : 0x00
437 txoff : off
438 softdcd : on
439 SLIP : off
442 The parameters have the following meaning:
444 speed:
445 The baudrate on this channel in bits/sec
447 Example: sccparam /dev/scc3 speed 9600
449 txdelay:
450 The delay (in units of 10 ms) after keying of the
451 transmitter, until the first byte is sent. This is usually
452 called "TXDELAY" in a TNC. When 0 is specified, the driver
453 will just wait until the CTS signal is asserted. This
454 assumes the presence of a timer or other circuitry in the
455 MODEM and/or transmitter, that asserts CTS when the
456 transmitter is ready for data.
457 A normal value of this parameter is 30-36.
459 Example: sccparam /dev/scc0 txd 20
461 persist:
462 This is the probability that the transmitter will be keyed
463 when the channel is found to be free. It is a value from 0
464 to 255, and the probability is (value+1)/256. The value
465 should be somewhere near 50-60, and should be lowered when
466 the channel is used more heavily.
468 Example: sccparam /dev/scc2 persist 20
470 slottime:
471 This is the time between samples of the channel. It is
472 expressed in units of 10 ms. About 200-300 ms (value 20-30)
473 seems to be a good value.
475 Example: sccparam /dev/scc0 slot 20
477 tail:
478 The time the transmitter will remain keyed after the last
479 byte of a packet has been transferred to the SCC. This is
480 necessary because the CRC and a flag still have to leave the
481 SCC before the transmitter is keyed down. The value depends
482 on the baudrate selected. A few character times should be
483 sufficient, e.g. 40ms at 1200 baud. (value 4)
484 The value of this parameter is in 10 ms units.
486 Example: sccparam /dev/scc2 4
488 full:
489 The full-duplex mode switch. This can be one of the following
490 values:
492 0: The interface will operate in CSMA mode (the normal
493 half-duplex packet radio operation)
494 1: Fullduplex mode, i.e. the transmitter will be keyed at
495 any time, without checking the received carrier. It
496 will be unkeyed when there are no packets to be sent.
497 2: Like 1, but the transmitter will remain keyed, also
498 when there are no packets to be sent. Flags will be
499 sent in that case, until a timeout (parameter 10)
500 occurs.
502 Example: sccparam /dev/scc0 fulldup off
504 wait:
505 The initial waittime before any transmit attempt, after the
506 frame has been queue for transmit. This is the length of
507 the first slot in CSMA mode. In full duplex modes it is
508 set to 0 for maximum performance.
509 The value of this parameter is in 10 ms units.
511 Example: sccparam /dev/scc1 wait 4
513 maxkey:
514 The maximal time the transmitter will be keyed to send
515 packets, in seconds. This can be useful on busy CSMA
516 channels, to avoid "getting a bad reputation" when you are
517 generating a lot of traffic. After the specified time has
518 elapsed, no new frame will be started. Instead, the trans-
519 mitter will be switched off for a specified time (parameter
520 min), and then the selected algorithm for keyup will be
521 started again.
522 The value 0 as well as "off" will disable this feature,
523 and allow infinite transmission time.
525 Example: sccparam /dev/scc0 maxk 20
527 min:
528 This is the time the transmitter will be switched off when
529 the maximum transmission time is exceeded.
531 Example: sccparam /dev/scc3 min 10
533 idle
534 This parameter specifies the maximum idle time in full duplex
535 2 mode, in seconds. When no frames have been sent for this
536 time, the transmitter will be keyed down. A value of 0 is
537 has same result as the fullduplex mode 1. This parameter
538 can be disabled.
540 Example: sccparam /dev/scc2 idle off # transmit forever
542 maxdefer
543 This is the maximum time (in seconds) to wait for a free channel
544 to send. When this timer expires the transmitter will be keyed
545 IMMEDIATELY. If you love to get trouble with other users you
546 should set this to a very low value ;-)
548 Example: sccparam /dev/scc0 maxdefer 240 # 2 minutes
551 txoff:
552 When this parameter has the value 0, the transmission of packets
553 is enable. Otherwise it is disabled.
555 Example: sccparam /dev/scc2 txoff on
557 group:
558 It is possible to build special radio equipment to use more than
559 one frequency on the same band, e.g. using several receivers and
560 only one transmitter that can be switched between frequencies.
561 Also, you can connect several radios that are active on the same
562 band. In these cases, it is not possible, or not a good idea, to
563 transmit on more than one frequency. The SCC driver provides a
564 method to lock transmitters on different interfaces, using the
565 "param <interface> group <x>" command. This will only work when
566 you are using CSMA mode (parameter full = 0).
567 The number <x> must be 0 if you want no group restrictions, and
568 can be computed as follows to create restricted groups:
569 <x> is the sum of some OCTAL numbers:
571 200 This transmitter will only be keyed when all other
572 transmitters in the group are off.
573 100 This transmitter will only be keyed when the carrier
574 detect of all other interfaces in the group is off.
575 0xx A byte that can be used to define different groups.
576 Interfaces are in the same group, when the logical AND
577 between their xx values is nonzero.
579 Examples:
580 When 2 interfaces use group 201, their transmitters will never be
581 keyed at the same time.
582 When 2 interfaces use group 101, the transmitters will only key
583 when both channels are clear at the same time. When group 301,
584 the transmitters will not be keyed at the same time.
586 Don't forget to convert the octal numbers into decimal before
587 you set the parameter.
589 Example: (to be written)
591 softdcd:
592 use a software dcd instead of the real one... Useful for a very
593 slow squelch.
595 Example: sccparam /dev/scc0 soft on
598 4. Problems
599 ===========
601 If you have tx-problems with your BayCom USCC card please check
602 the manufacturer of the 8530. SGS chips have a slightly
603 different timing. Try Zilog... A solution is to write to register 8
604 instead to the data port, but this won't work with the ESCC chips.
605 *SIGH!*
607 A very common problem is that the PTT locks until the maxkeyup timer
608 expires, although interrupts and clock source are correct. In most
609 cases compiling the driver with CONFIG_SCC_DELAY (set with
610 make config) solves the problems. For more hints read the (pseudo) FAQ
611 and the documentation coming with z8530drv-utils.
613 I got reports that the driver has problems on some 386-based systems.
614 (i.e. Amstrad) Those systems have a bogus AT bus timing which will
615 lead to delayed answers on interrupts. You can recognize these
616 problems by looking at the output of Sccstat for the suspected
617 port. If it shows under- and overruns you own such a system.
619 Delayed processing of received data: This depends on
621 - the kernel version
623 - kernel profiling compiled or not
625 - a high interrupt load
627 - a high load of the machine --- running X, Xmorph, XV and Povray,
628 while compiling the kernel... hmm ... even with 32 MB RAM ... ;-)
629 Or running a named for the whole .ampr.org domain on an 8 MB
630 box...
632 - using information from rxecho or kissbridge.
634 Kernel panics: please read /linux/README and find out if it
635 really occurred within the scc driver.
637 If you cannot solve a problem, send me
639 - a description of the problem,
640 - information on your hardware (computer system, scc board, modem)
641 - your kernel version
642 - the output of cat /proc/net/z8530
644 4. Thor RLC100
645 ==============
647 Mysteriously this board seems not to work with the driver. Anyone
648 got it up-and-running?
651 Many thanks to Linus Torvalds and Alan Cox for including the driver
652 in the Linux standard distribution and their support.
654 Joerg Reuter ampr-net: dl1bke@db0pra.ampr.org
655 AX-25 : DL1BKE @ DB0ABH.#BAY.DEU.EU
656 Internet: jreuter@yaina.de
657 WWW : http://yaina.de/jreuter