Paul Jackson wrote:
Nick wrote:
And is the pair of operators:
task_lock(current), task_unlock(current)
really that much worse than the pair of operators
...
preempt_disable, preempt_enable
That part still surprises me a little. Is there enough difference in
the performance between:
1) task_lock, which is a spinlock on current->alloc_lock and
2) rcu_read_lock, which is .preempt_count++; barrier()
to justify a separate slab cache for cpusets and a little more code?
For all I know (not much) the task_lock might actually be cheaper ;).
But on a preempt kernel the spinlock must disable preempt as well!
Not to mention that a spinlock is an atomic op (though that is getting
cheaper these days) + 2 memory barriers (getting more expensive).
The semaphore down means doing an atomic_dec_return(), which imposes
a memory barrier, right?
Yep.
--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
