- turns balloon into a driver that attaches to xenbus(4). This allows to
disable the functionality either at compile time or boot time via
userconf(4). Driver can implement detach or pmf(9) hooks if deemed
necessary.
- keeps Cherry's locking model, but simplify it a bit. There is now
only one target value serialized inside balloon, we do not feedback
alternative value to Xenstore (clients are not expected to see its value
evolve behind their back, and can't do much about that either)
- implements min threshold; this is an admin-settable value that tells
driver to "not balloon below this threshold." This can be used by domain
to keep memory reservations, useful if activity is expected in the near
future.
- in addition to min threshold, the driver implements internally a
safeguard value (uvmexp.freemin + 1MiB), so that admin cannot
inadvertently set min to a very low value forcing domain into heavy
memory pressure and swapping.
- create the sysctl(8) kern.xen.balloon tree. 4 nodes are actually present
(values are in KiB):
- min: (rw) an admin-settable value that prevents ballooning below this
mark
- max: (ro) the maximum size for reservation, as set by xm(1) mem-max.
- current: (ro) the current reservation for domain.
- target: (rw) the targetted reservation for domain.
- fix a few limitations here and there, most notably the max_reservation
hypercall, and KiB vs pages representations at interfaces.
The driver is still turned off by default. Enabling it would need more
approval, especially from bouyer@, cherry@ and cegger@.
FWIW: tested it two days long, from amd64 dom0 (with dom0 ballooning
enabled for xend), and bunch of domUs. Did not notice anything suspicious.
XXX it still has one big limitation: it cannot hotplug memory pages in
uvm(9) if they were not present beforehand. Example: ballooning above
physmem will give more pages to domain but it won't use it to serve
allocations, unless we teach uvm(9) how to handle the extra pages.
reversing the sense of the associated test and using the big block I
moved a couple versions back (and didn't reindent on purpose) as the
body of the if statement.
There are now no gotos in namei_oneroot, only normal loop logic.
now be changed to a loop break and another null test and goto outside
the loop. In neither of the other two cases for exiting the loop can
foundobj be null.
has an unconditional loop break at the end this can be done safely,
now that the other loop break has been patched out.
Add a spurious set of braces to preserve the indent for the moment.
continue.
This runs the "are we mounted?" test on every directory instead of
only sometimes; however, it's not exactly an expensive test (null
pointer check) and the prior logic wasn't exactly sensible -- it
checked at the beginning and after following a symlink but, for some
reason, not after crossing a mount point.
so nfsd no longer needed to do a lookup() call immediately afterwards
to retrieve the newly created object.
Since that change there has been no way for ISSYMLINK to be set upon
return from VOP_MKNOD (or before the call to VOP_MKNOD either) so
remove the test for it and associated block of dead code.
(I do not understand how this code was reachable before then either.
The logic in question is only reached if no object by that name
existed, and there's no reasonable way that a successful call to
VOP_MKNOD should ever create a symlink. The code appears to come from
4.4lite; maybe they had locking bugs?)
I2C_OP_STOP_P(), but all read-transfers have to be finished that way.
Otherwise a chip might hang after a read-operation without stop.
Removed sc_start from the softc structure, which is unused.
