Messages in this thread | | | Date | Thu, 7 Jun 2018 16:49:26 -0700 | From | Matthew Wilcox <> | Subject | Re: [RFC] IB/mad: Use IDR instead of per-port list |
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On Thu, Jun 07, 2018 at 04:26:46PM -0600, Jason Gunthorpe wrote: > On Thu, Jun 07, 2018 at 12:08:32PM -0700, Matthew Wilcox wrote: > > > > Hans reports a bug where the mlx4 driver uses the MSB of the agent number > > to store slave number, meaning we can only use agent numbers up to 2^24. > > Fix this by using an IDR to assign the agent numbers and also look up the > > agent when a MSD packet is received. > > > > I've changed the locking substantially, so this may well have a > > performance issue. There are a few different possibilities for fixing > > that, including moving to an RCU-based lookup. > > I do like this better than the last series.. > > This are is somewhat performance sensitive and it would be nice to > avoid this global lock.
OK, I wasn't sure whether it was worth it.
> What about using a read/write spinlock instead of the IDR internal > lock? Then all the per-port reading threads calling find_mad_agent can > run concurrently..
It'd be better to switch to RCU ... the IDR is RCU-safe, but the version/class/method or OUI match isn't. Do you have any feeling on the relative frequency of the two types of "routing"?
Actually, I think we can use the radix tree data structure for the version/class/method too ... that's going to take a little more work.
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