view Documentation/networking/smc9.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
2 SMC 9xxxx Driver
3 Revision 0.12
4 3/5/96
5 Copyright 1996 Erik Stahlman
6 Released under terms of the GNU General Public License.
8 This file contains the instructions and caveats for my SMC9xxx driver. You
9 should not be using the driver without reading this file.
11 Things to note about installation:
13 1. The driver should work on all kernels from 1.2.13 until 1.3.71.
14 (A kernel patch is supplied for 1.3.71 )
16 2. If you include this into the kernel, you might need to change some
17 options, such as for forcing IRQ.
20 3. To compile as a module, run 'make' .
21 Make will give you the appropriate options for various kernel support.
23 4. Loading the driver as a module :
25 use: insmod smc9194.o
26 optional parameters:
27 io=xxxx : your base address
28 irq=xx : your irq
29 ifport=x : 0 for whatever is default
30 1 for twisted pair
31 2 for AUI ( or BNC on some cards )
33 How to obtain the latest version?
35 FTP:
36 ftp://fenris.campus.vt.edu/smc9/smc9-12.tar.gz
37 ftp://sfbox.vt.edu/filebox/F/fenris/smc9/smc9-12.tar.gz
40 Contacting me:
41 erik@mail.vt.edu