view Documentation/pcmcia/devicetable.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 Matching of PCMCIA devices to drivers is done using one or more of the
2 following criteria:
4 - manufactor ID
5 - card ID
6 - product ID strings _and_ hashes of these strings
7 - function ID
8 - device function (actual and pseudo)
10 You should use the helpers in include/pcmcia/device_id.h for generating the
11 struct pcmcia_device_id[] entries which match devices to drivers.
13 If you want to match product ID strings, you also need to pass the crc32
14 hashes of the string to the macro, e.g. if you want to match the product ID
15 string 1, you need to use
17 PCMCIA_DEVICE_PROD_ID1("some_string", 0x(hash_of_some_string)),
19 If the hash is incorrect, the kernel will inform you about this in "dmesg"
20 upon module initialization, and tell you of the correct hash.
22 You can determine the hash of the product ID strings by catting the file
23 "modalias" in the sysfs directory of the PCMCIA device. It generates a string
24 in the following form:
25 pcmcia:m0149cC1ABf06pfn00fn00pa725B842DpbF1EFEE84pc0877B627pd00000000
27 The hex value after "pa" is the hash of product ID string 1, after "pb" for
28 string 2 and so on.
30 Alternatively, you can use crc32hash (see Documentation/pcmcia/crc32hash.c)
31 to determine the crc32 hash. Simply pass the string you want to evaluate
32 as argument to this program, e.g.:
33 $ ./crc32hash "Dual Speed"