[patch] sched_[set|get]_affinity() syscall, 2.4.15-pre9

[Ingo Molnar]

  This message is in MIME format.  The first part should be readable text,
  while the remaining parts are likely unreadable without MIME-aware tools.
  Send mail to [e-mail] for more info.

--8323328-295900366-1006347495=:10030
Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
Content-ID: <[e-mail]>

the attached set-affinity-A1 patch is relative to the scheduler
fixes/cleanups in 2.4.15-pre9. It implements the following two
new system calls:

 asmlinkage int sys_sched_set_affinity(pid_t pid, unsigned int mask_len,
    unsigned long *new_mask_ptr);

 asmlinkage int sys_sched_get_affinity(pid_t pid, unsigned int
    *user_mask_len_ptr, unsigned long *user_mask_ptr);

as a testcase, softirq.c is updated to use this mechanizm, plus see the
attached loop_affine.c code.

the sched_set_affinity() syscall also ensures that the target process will
run on the right CPU (or CPUs).

I think this interface is the right way to expose user-selectable affinity
to user-space - there are more complex affinity interfaces in existence,
but i believe that the discovery of actual caching hierarchy is and should
be up to a different mechanizm, i dont think it should be mixed into the
affinity syscalls. Using a mask of linear CPU IDs is IMO sufficient to
express user-space affinity wishes.

There are no security issues wrt. cpus_allowed, so these syscalls are
available to every process. (there are permission restrictions of course,
similar to those of existing scheduler syscalls.)

sched_get_affinity(pid, &mask_len, NULL) can be used to query the kernel's
supported CPU bitmask length. This should help us in achieving a stable
libc interface once we get over the 32/64 CPUs limit.

the attached loop_affine.c code tests both syscalls:

 mars:~> ./loop_affine
 current process's affinity: 4 bytes mask, value 000000ff.
 trying to set process: affinity to 00000001.
 current process's affinity: 4 bytes mask, value 00000001.
 speed: 2162052 loops.
 speed: 2162078 loops.
 [...]

i've tested the patch on both SMP and UP systems. On UP the syscalls are
pretty pointless, but they show that the internal state of the scheduler
folds nicely into the UP case as well:

 mars:~> ./loop_affine
 current process's affinity: 4 bytes mask, value 00000001.
 trying to set process: affinity to 00000001.
 current process's affinity: 4 bytes mask, value 00000001.
 speed: 2160880 loops.
 speed: 2160511 loops.
 [...]

comments? Is there any reason to do a more complex interface than this?

	Ingo

--8323328-295900366-1006347495=:10030
Content-Type: TEXT/PLAIN; charset=US-ASCII; name="set-affinity-2.4.15-A1"
Content-Transfer-Encoding: BASE64
Content-ID: <[e-mail]>
Content-Description: 
Content-Disposition: attachment; filename="set-affinity-2.4.15-A1"
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--8323328-295900366-1006347495=:10030
Content-Type: TEXT/PLAIN; charset=US-ASCII; name="loop_affine.c"
Content-Transfer-Encoding: BASE64
Content-ID: <[e-mail]>
Content-Description: 
Content-Disposition: attachment; filename="loop_affine.c"
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--8323328-295900366-1006347495=:10030--