On 02/27/2013 11:49 PM, Linus Torvalds wrote:
On Wed, Feb 27, 2013 at 8:06 PM, Davidlohr Bueso <davidlohr.bueso@xxxxxx> wrote:The attached file shows how the amount of sys time used by the ipc lock for a 4 and 8 socket box.I have to say, even with the improvements, that looks pretty disgusting. It really makes me wonder if that thing couldn't be done better some way. Is it the SysV semaphores that this all ends up using, or what? That said, I think the IPC layer is just about the perfect candidate for things like this, because I'm afraid that nobody is ever going to fix it.
There's more to it than that. Userspace expects the IPC layer to provide exclusion and/or serialization. That makes it a rather poor candidate for parallelism. Btw, the IPC lock is already fairly fine grained. One ipc lock is allocated for each set of semaphores allocated through sys_semget. Looking up those semaphores in the namespace, when they are used later, is done under RCU. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html