On Wed, Jun 15, 2016 at 03:31:51PM -0400, Waiman Long wrote: > On 06/15/2016 01:43 PM, Peter Zijlstra wrote: > >On Tue, Jun 14, 2016 at 06:48:08PM -0400, Waiman Long wrote: > >>even the reduced maximum of about 16k (32-bit) or 1G (64-bit) should > >>be more than enough for the foreseeable future. > >So what happens if I manage to create 16k+ threads on my 32bit kernel > >and get them all to do mmap() or so at the same time. > > > >That doesn't seem too far fetched. > > > >Then again, with double that (the current limit) that doesn't seem > >impossible either. > > To hit the limit, we need to have all the threads calling down_write() at > exactly the same instance in time which, I think, is pretty hard to do. > Also, I don't believe you will ever see a 16k-cpu massive SMP system running > on 32-bit kernel. I can imagine such a system running on 64-bit kernel, but > certainly not 32-bit. Ah, so I thought we kept the WRITE_BIAS while blocking, which we don't. But if they all get preempted before we undo the WRITE_BIAS then 1 CPU will be able to trigger this. However utterly unlikely. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
