On Tue, 04 Jul 2017, Thomas Gleixner wrote:
On Tue, 4 Jul 2017, Davidlohr Bueso wrote:
On Tue, 04 Jul 2017, Davidlohr Bueso wrote:
> As a side effect you end up optimizing get/put_online_mems() at the cost
> of more overhead for the actual hotplug operation, which is rare and of less
> performance importance.
So nm this, the reader side actually gets _more_ expensive with pcpu-rwsems
due to at least two full barriers for each get/put operation.
Compared to a mutex_lock/unlock() pair on a global mutex ....
Ah, right, I was thrown off the:
if (mem_hotplug.active_writer == current)
return;
checks, which is only true within hotplug_begin/end. So normally we'd take
the lock, which was my first impression. Sorry for the noise.
Thanks,
Davidlohr
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
