These are of use to userland code which previously depended on the
hard-coded values of LABELSECTOR and LABELOFFSET to figure out the
location of the disklabel for a particular platform.
With the introduction of umbrella ports such as evbarm, evbmips, etc,
the location of the disklabel may vary between kernels for the same
MACHINE. This sysctl will allow userland programs to remain independent
of the particular flavour of MACHINE in such cases.
that can be used to block a process after fork(2) or exec(2) calls. The
new process is created in the SSTOP state and is never scheduled for running.
This feature is designed so that it is esay to attach the process using gdb
before it has done anything.
It works also with sproc, kthread_create, clone...
for FreeBSD project. Besides huge speed boost compared with socketpair-based
pipes, this implementation also uses pagable kernel memory instead of mbufs.
Significant differences to FreeBSD version:
* uses uvm_loan() facility for direct write
* async/SIGIO handling correct also for sync writer, async reader
* limits settable via sysctl, amountpipekva and nbigpipes available via sysctl
* pipes are unidirectional - this is enforced on file descriptor level
for now only, the code would be updated to take advantage of it
eventually
* uses lockmgr(9)-based locks instead of home brew variant
* scatter-gather write is handled correctly for direct write case, data
is transferred by PIPE_DIRECT_CHUNK bytes maximum, to avoid running out of kva
All FreeBSD/NetBSD specific code is within appropriate #ifdef, in preparation
to feed changes back to FreeBSD tree.
This pipe implementation is optional for now, add 'options NEW_PIPE'
to your kernel config to use it.
each of the basic types (anonymous data, executable image, cached files)
and prevent the pagedaemon from reusing a given page if that would reduce
the count of that type of page below a sysctl-setable minimum threshold.
the thresholds are controlled via three new sysctl tunables:
vm.anonmin, vm.vnodemin, and vm.vtextmin. these tunables are the
percentages of pageable memory reserved for each usage, and we do not allow
the sum of the minimums to be more than 95% so that there's always some
memory that can be reused.
