:While I am here, can the schedulers allow userspace to specify a cpumask
:a thread is willing to run on, some highend software e.g database
:systems may want this feature, as they are intend to manager their
:CPU locality like they did for RAW device.
:
This would be a good mini-project. I think it would be quit easy
to add this level of control. The current BSD4 scheduler implementation
uses cpu masks as part of its core algorithm.
If someone would like to take on this project I recommend tying the
feature into usched_set(). Maybe change it from:
int usched_set(const char *name, int flags);
To something more generic:
int usched_set(pid_t pid, int cmd, void *data, int bytes)
USCHED_SET_SCHEDULER
Set the scheduler for the specified process based on the
passed string. data should be a string pointer and bytes
should be the length of the string not-including the
zero terminator.
Currently only "bsd4" is supported.
USCHED_ADD_CPU
Add the cpu id pointed to by the data to the set of
cpu's that the process is allowed to run on. e.g.:
int cpu = blah;
usched_set(getpid(), &cpu, sizeof(cpu));
USCHED_DEL_CPU
Remove the cpu id from the set of cpus the process is
allowed to run on.
This command will fail if the removal of the cpu id would
result in the process not being able to run on any cpus.
USCHED_SET_CPU
Make the specified cpuid the only cpu that the process is
allowed to run on.
I think it would be a very easy project for someone to clean up
usched_set() and then add the cpu masking features. For an initial
implementation the 'pid' would have to be restricted to just the calling
process's pid (else it gets quite messy). But all children would inherit
the scheduler setup so it would be easy to test.
If someone does the work to get it to that point I can sit down and
do the rest... allowing foreign pids, and doing the nitpicky stuff
in usched_bsd4.c to actually make cpu masking work. All I am asking
for is that someone build the framework leading up to that point.
-Matt
Matthew Dillon
<[EMAIL PROTECTED]>
